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Using an 𝑒+𝑒− collision data sample of (27.08±0.14)×108 𝜓(3686) events collected by the BESIII detector, we report the first observation of 𝜒𝑐𝐽→Ω−¯Ω+ (𝐽=0, 1, 2) decays with significances of 5.6𝜎, 6.4𝜎, and 18𝜎, respectively, where the 𝜒𝑐𝐽 mesons are produced in the radiative 𝜓(3686) decays. The branching fractions are determined to be ℬ(𝜒𝑐0→Ω−¯Ω+) = (3.51±0.54±0.29)×10−5, ℬ(𝜒𝑐1→Ω−¯Ω+)=(1.49±0.23±0.10)×10−5, and ℬ(𝜒𝑐2→Ω−¯Ω+)=(4.52±0.24±0.18)×10−5, where the first and second uncertainties are statistical and systematic, respectively.
Using (1.0087±0.0044)×1010 𝐽/𝜓 events collected by the BESIII detector at the BEPCII collider, we report the first search for the baryon and lepton number violating decays Ξ0→𝐾−𝑒+ with Δ(𝐵−𝐿)=0 and Ξ0→𝐾+𝑒− with |Δ(𝐵−𝐿)|=2, where 𝐵 (𝐿) is the baryon (lepton) number. While no signal is observed, the upper limits on the branching fractions of these two decays are set to ℬ(Ξ0→𝐾−𝑒+)<3.6×10−6 and ℬ(Ξ0→𝐾+𝑒−)<1.9×10−6 at the 90% confidence level, respectively. These results offer a direct probe of baryon number violating interactions involving a strange quark.
The Ξ0 asymmetry parameters are measured using entangled quantum Ξ0 − Ξ¯ 0 pairs from a sample of ð448.1 2.9Þ × 106 ψð3686Þ events collected with the BESIII detector at BEPCII. The relative phase between the transition amplitudes of the Ξ0Ξ¯ 0 helicity states is measured to be ΔΦ ¼ −0.050 0.150 0.020 rad, which implies that there is no obvious polarization at the current level of statistics. The decay parameters of the Ξ0 hyperon ðαΞ0 ; αΞ¯ 0 ; ϕΞ0 ; ϕΞ¯ 0 Þ and the angular distribution parameter ½αψð3686Þ and ΔΦ are measured simultaneously for the first time. In addition, the CP asymmetry observables are determined to be AΞ0 CP ¼ ðαΞ0 þ αΞ¯ 0 Þ=ðαΞ0 − αΞ¯ 0 Þ ¼ −0.007 0.082 0.025 and ΔϕΞ0 CP ¼ ðϕΞ0 þ ϕΞ¯ 0 Þ=2 ¼ −0.079 0.082 0.010 rad, which are consistent with CP conservation.
We report on the first search for ¯Λ−Λ oscillations in the decay 𝐽/𝜓→𝑝𝐾−¯Λ+c.c. by analyzing 1.31×109 𝐽/𝜓 events accumulated with the BESIII detector at the BEPCII collider. The 𝐽/𝜓 events are produced using 𝑒+𝑒− collisions at a center of mass energy √𝑠=3.097 GeV. No evidence for hyperon oscillations is observed. The upper limit for the oscillation rate of ¯Λ to Λ hyperons is determined to be 𝒫(Λ)=[ℬ(𝐽/𝜓→𝑝𝐾−Λ+c.c.)/ℬ(𝐽/𝜓→𝑝𝐾−¯Λ+c.c.)]<4.4×10−6 corresponding to an oscillation parameter 𝛿𝑚Λ¯Λ of less than 3.8×10−18 GeV at the 90% confidence level.
The theoretical and experimental investigation of exotic hadrons like tetraquarks is an important branch of modern elementary particle physics. In this thesis I investigate different four-quark systems using lattice QCD and search for evidence of stable tetraquark states or resonances.
Lattice QCD as a non-perturbative approach to QCD allows an accurate and reliable determination of the masses of strongly bound hadrons.
However, most tetraquarks appear as weakly bound states or resonances, which makes a theoretical investigation using lattice QCD difficult due to the finite spatial volume. A rigorous treatment of such systems is feasible using the so-called Lüscher method. This allows to calculate the scattering amplitude based on the finite-volume energy spectrum determined in a lattice QCD calculation. Similarly to the analysis of experimental data, this scattering amplitude can be used to determine the binding energies of bound states or the masses and decay widths of resonances in the infinite volume.
In my work I calculate the low-energy energy spectra of different four-quark systems and use - if necessary - the Lüscher method to determine the masses of potential tetraquark states.
I focus on systems consisting of two heavy antiquarks and two light quarks, where at least one of the heavy antiquarks is a bottom quark.
Even though such tetraquarks have not yet been experimentally detected, they are considered promising candidates for particles that are stable with respect to the strong interaction.
A decisive step for successfully calculating low-lying energy levels for such four-quark systems is a carefully chosen set of creation operators, which represent the physical states most accurately. In addition to operators that generate a local structure where all four quarks are located at the same space-time point, I also use so-called scattering operators that resemble two spatially separated mesons. These scattering operators turned out to be relevant for successfully determining the lowest energy levels and are therefore essential, especially if a Lüscher analysis is carried out.
In my work, I considered two different lattice setups to study the four-quark systems $\bar{b}\bar{b}ud$ with $I(J^P)=0(1^+) $, $\bar{b}\bar{b}us$ with $J^P=1^+ $ and $\bar{b}\bar{c}ud$ with $I(J^P)=0(0^+) $ and $I(J^P)=0(1^+) $ and to predict potential tetraquark states. In both setups, I considered scattering operators. While in the first setup I used them only as annihilation operators, in the second setup they were included both as creation and annihilation operators. Additionally, in the second lattice setup, I performed a simplified investigation of the $\bar{b}\bar{b}ud$ system with $I(J^P)=0(1^-) $, which is a potential candidate for a tetraquark resonance. The results of the investigation of the mentioned four-quark systems can be summarized as follows:
For the $ \bar{b}\bar{b}ud $ four-quark system with $ I(J^P)=0(1^+) $ I found a deeply bound ground state slightly more than $ 100\,\textrm{MeV} $ below the lowest meson-meson threshold. The existence of a corresponding $\bar{b}\bar{b}ud$ tetraquark in the infinite volume was confirmed using a Lüscher analysis and possible systematic errors due to the use of lattice QCD were taken into account.
Similar results were obtained for the $ \bar{b}\bar{b}us $ four-quark system with $ J^P=1^+ $. Again, I found a ground state well below the lowest meson-meson threshold, but slightly weaker bound than for the $ \bar{b}\bar{b}ud $ system. Effects due to the finite volume turned out to be negligible for this system, as already predicted for the $ \bar{b}\bar{b}ud $ system. \item For the $ \bar{b}\bar{c}ud $ four-quark systems with $ (J^P)=0(0^+) $ and $ (J^P)=0(1^+) $ I was able to rule out the existence of a deeply bound tetraquark states based on the energy spectrum in the finite volume. However, by means of a scattering analysis using the Lüscher method, I found evidence a broad resonance for both channels.
In the case of the $ \bar{b}\bar{b}ud $ four-quark system with $ I(J^P)=0(1^-) $, I could neither confirm the existence of a resonance, nor rule out its existence with certainty.
In particular, my investigations showed that the results of the two different lattice simulations are consistent. The theoretical prediction of the bound tetraquark states $\bar{b}\bar{b}ud$ and $\bar{b}\bar{b}us$ as well as the tetraquark resonances in the $\bar{b}\bar{c}ud$ system in this work represent an important contribution to the future experimental search for exotic hadrons and can support the discovery of previously unobserved particles.
We search for an axion-like particle (ALP) a through the process ψ(3686)→π+π−J/ψ, J/ψ→γa, a→γγ in a data sample of (2.71±0.01)×109 ψ(3686) events collected by the BESIII detector. No significant ALP signal is observed over the expected background, and the upper limits on the branching fraction of the decay J/ψ→γa and the ALP-photon coupling constant gaγγ are set at 95% confidence level in the mass range of 0.165≤ma≤2.84GeV/c2. The limits on B(J/ψ→γa) range from 8.3×10−8 to 1.8×10−6 over the search region, and the constraints on the ALP-photon coupling are the most stringent to date for 0.165≤ma≤1.468GeV/c2.
Using data samples with an integrated luminosity of 22.42 fb−1 collected by the BESIII detector operating at the BEPCII storage ring, we measure the cross sections of the $e^{+}e^{-}\rightarrow\etaJ/\psi$ process at center-of-mass energies from 3.808 to 4.951 GeV. Three structures are observed in the line shape of the measured cross sections. A maximum-likelihood fit with ψ(4040), two additional resonances, and a non-resonant component is performed. The mass and width of the first additional state are (4219.7±2.5±4.5)MeV/c2 and (80.7±4.4±1.4)MeV, respectively, consistent with the ψ(4230). For the second state, the mass and width are (4386±13±17)MeV/c2 and (177±32±13)MeV, respectively, consistent with the ψ(4360). The first uncertainties are statistical and the second ones are systematic. The statistical significance of ψ(4040) is 8.0σ and those for ψ(4230) and ψ(4360) are more than 10.0σ.
Using a sample of (10087±44)×106 J/ψ events, which is about fifty times larger than that was previously analyzed, a further investigation on the J/ψ→γ3(π+π−) decay is performed. A significant distortion at 1.84 GeV/c2 in the line-shape of the 3(π+π−) invariant mass spectrum is observed for the first time, which is analogous to the behavior of X(1835) and could be resolved by two overlapping resonant structures, X(1840) and X(1880). The new state X(1880) is observed with a statistical significance of 14.7σ. The mass and width of X(1880) are determined to be 1882.1±1.7±0.7 MeV/c2 and 30.7±5.5±2.4 MeV, respectively, which indicates the existence of a pp¯ bound state.
Based on (10.09±0.04)×109 J/ψ events collected with the BESIII detector operating at the BEPCII collider, a partial wave analysis of the decay J/ψ→ϕπ0η is performed. We observe for the first time two new structures on the ϕη invariant mass distribution, with statistical significances of 24.0σ and 16.9σ; the first with JPC = 1+−, mass M = (1911 ± 6 (stat.) ± 14 (sys.))~MeV/c2, and width Γ= (149 ± 12 (stat.) ± 23 (sys.))~MeV, the second with JPC = 1−−, mass M = (1996 ± 11 (stat.) ± 30 (sys.))~MeV/c2, and width Γ = (148 ± 16 (stat.) ± 66 (sys.))~MeV. These measurements provide important input for the strangeonium spectrum. In addition, the f0(980)−a0(980)0 mixing signal in J/ψ→ϕf0(980)→ϕa0(980)0 and the corresponding electromagnetic decay J/ψ→ϕa0(980)0 are measured with improved precision, providing crucial information to understand the nature of a0(980)0 and f0(980).
Based on (10.09±0.04)×109 J/ψ events collected with the BESIII detector operating at the BEPCII collider, a partial wave analysis of the decay J/ψ→ϕπ0η is performed. We observe for the first time two new structures on the ϕη invariant mass distribution, with statistical significances of 24.0σ and 16.9σ; the first with JPC = 1+−, mass M = (1911 ± 6 (stat.) ± 14 (sys.))~MeV/c2, and width Γ= (149 ± 12 (stat.) ± 23 (sys.))~MeV, the second with JPC = 1−−, mass M = (1996 ± 11 (stat.) ± 30 (sys.))~MeV/c2, and width Γ = (148 ± 16 (stat.) ± 66 (sys.))~MeV. These measurements provide important input for the strangeonium spectrum. In addition, the f0(980)−a0(980)0 mixing signal in J/ψ→ϕf0(980)→ϕa0(980)0 and the corresponding electromagnetic decay J/ψ→ϕa0(980)0 are measured with improved precision, providing crucial information to understand the nature of a0(980)0 and f0(980).
Using 7.33 fb−1 of e+e− collision data collected by the BESIII detector at center-of-mass energies between 4.128 and 4.226~GeV, we observe for the first time the decay D±s→ωπ±η with a statistical significance of 7.6σ. The measured branching fraction of this decay is (0.54±0.12±0.04)%, where the first uncertainty is statistical and the second is systematic.
Evidence for the singly Cabibbo suppressed decay Λ+c→pπ0 is reported for the first time with a statistical significance of 3.7σ based on 6.0 fb−1 of e+e− collision data collected at center-of-mass energies between 4.600 and 4.843 GeV with the BESIII detector at the BEPCII collider. The absolute branching fraction of Λ+c→pπ0 is measured to be (1.56+0.72−0.58±0.20)×10−4, which distinctly exceeds the upper limit measured by Belle experiment. Combining with the branching fraction of Λ+c→nπ+, (6.6±1.3)×10−4, the ratio of the branching fractions of Λ+c→nπ+ and Λ+c→pπ0 is calculated to be 3.2+2.2−1.2. As an important input for the theoretical models describing the decay mechanisms of charmed baryons, our result indicates that the non-factorizable contributions play an essential role and their interference with the factorizable contributions should not be significant. In addition, the absolute branching fraction of Λ+c→pη is measured to be (1.63±0.31stat±0.11syst)×10−3, which is consistent with previous measurements.
Evidence for the singly Cabibbo suppressed decay Λ+c→pπ0 is reported for the first time with a statistical significance of 3.7σ based on 6.0 fb−1 of e+e− collision data collected at center-of-mass energies between 4.600 and 4.843 GeV with the BESIII detector at the BEPCII collider. The absolute branching fraction of Λ+c→pπ0 is measured to be (1.56+0.72−0.58±0.20)×10−4. Combining with the branching fraction of Λ+c→nπ+, (6.6±1.2±0.4)×10−4, the ratio of the branching fractions Λ+c→nπ+ and Λ+c→pπ0 is calculated to be 4.2+2.2−1.9; this is an important input for the understanding of the decay mechanisms of charmed baryons. In addition, the absolute branching fraction of Λ+c→pη is measured to be (1.63±0.31stat±0.11syst)×10−3, which is consistent with previous measurements.
Based on 4.5 fb−1 data taken at seven center-of-mass energies ranging from 4.600 to 4.699 GeV with the BESIII detector at the BEPCII collider, we measure the branching fractions of Λ + c → Σ + + hadrons relative to Λ + c → Σ +π +π −. Combining with the world average branching fraction of Λ + c → Σ +π +π −, their branching fractions are measured to be (0.377 ± 0.042 ± 0.020 ± 0.021)% for Λ + c → Σ +K+K−, (0.200 ± 0.023 ± 0.011 ± 0.011)% for Λ + c → Σ+K+π−, (0.414 ± 0.080 ± 0.030 ± 0.023)% for Λ + c → Σ +φ and (0.197 ± 0.036 ± 0.009 ± 0.011)% for Λ + c → Σ +K+K−(non-φ). In all the above results, the first uncertainties are statistical, the second are systematic and the third are from external input of the branching fraction of Λ + c → Σ +π +π −. Since no signal for Λ + c → Σ +K+π−π 0 is observed, the upper limit of its branching fraction is determined to be 0.13% at the 90% confidence level.
We search for the semi-leptonic decays Λ + c → Λπ+π−e+νe and Λ + c → pK0 Sπ−e+νe in a sample of 4.5 fb−1 of e+e− annihilation data collected in the center-of-mass energy region between 4.600 GeV and 4.699 GeV by the BESIII detector at the BEPCII. No significant signals are observed, and the upper limits on the decay branching fractions are set to be B(Λ+c → Λπ+π−e+νe ) < 3.9 × 10−4 and B(Λ + c → pK0Sπ−e+νe ) < 3.3 × 10−4 at the 90% confidence level, respectively.
We present cross sections for the reaction e+e−→K0SK0L at center-of-mass energies ranging from 3.51 GeV to 4.95 GeV using data samples collected in the BESIII experiment, corresponding to a total integrated luminosity of 26.5 fb−1. The ratio of neutral-to-charged kaon form factors at large momentum transfers (12 GeV2<Q2<25 GeV2) is determined to be 0.21±0.01, which indicates a small but significant effect of flavor-SU(3) breaking in the kaon wave function, and consequently excludes the possibility that flavor-SU(3) breaking is the primary reason for the strong experimental violation of the pQCD prediction |F(π±)|/|F(K±)|=f2π/f2K, where F(π±) and F(K±) are the form factors, and fπ and fK are the decay constants of charged pions and kaons, respectively. We also observe a significant signal for the charmless decay ψ(3770)→K0SK0L for the first time. Within a 1σ contour of the likelihood value, the the branching fraction for ψ(3770)→K0SK0L is determined to be B=(2.63+1.40−1.59)×10−5, and the relative phase between the continuum and ψ(3770) amplitudes is ϕ=(−0.39+0.05−0.10)π. The branching fraction is in good agreement with the S- and D-wave charmonia mixing scheme proposed in the interpretation of the "ρπ puzzle" between J/ψ and ψ(3686) decays.
A search has been performed for the semileptonic decays D0→K0SK−e+νe, D+→K0SK0Se+νe and D+→K+K−e+νe, using 7.9 fb−1 of e+e− annihilation data collected at the center-of-mass energy s√=3.773 GeV by the BESIII detector operating at the BEPCII collider. No significant signals are observed, and upper limits are set at the 90\% confidence level of 2.13×10−5, 1.54×10−5 and 2.10×10−5 for the branching fractions of D0→K0SK−e+νe, D+→K0SK0Se+νe and D+→K+K−e+νe, respectively.
The Heidelberg Ion-Beam Therapy Centre (HIT) provides proton, helium, and carbon-ion beams with different energies and intensities for cancer treatment and oxygen-ion beams for experiments. For several experiments and possible future applications, such as helium ion beam radiography, a low-intensity ion beam monitor integrated into the dose delivery feedback system for the accelerator control is a necessary pre-requisite. The updated 2D prototype for this purpose consists of scintillating fibres with enhanced radiation hardness, silicon photomultipliers (SiPMs) to amplify the emitted light, and a dedicated front-end readout system (FERS) to process and record the generated signals. This setup was tested successfully on monitoring ion-beam position and profile horizontally and vertically, as well as the beam intensity, for all four ion types with energies from 50 to 430 MeV/u and intensities from 1E2 to 1E7 ions/s. Additionally, time-of-arrival (ToA) measurements on single ions have been successfully performed for a limited intensity range, allowing for ion tracking in a further update. This will reduce noise, and will also improve the accuracy and usability of ion radiography.
The free energy of TAP-solutions for the SK-model of mean field spin glasses can be expressed as a nonlinear functional of local terms: we exploit this feature in order to contrive abstract REM-like models which we then solve by a classical large deviations treatment. This allows to identify the origin of the physically unsettling quadratic (in the inverse of temperature) correction to the Parisi free energy for the SK-model, and formalizes the true cavity dynamics which acts on TAP-space, i.e. on the space of TAP-solutions. From a non-spin glass point of view, this work is the first in a series of refinements which addresses the stability of hierarchical structures in models of evolving populations.
Off-central heavy-ion collisions are known to feature magnetic fields with magnitudes and characteristic gradients corresponding to the scale of the strong interactions. In this work, we employ equilibrium lattice simulations of the underlying theory, QCD, involving similar inhomogeneous magnetic field profiles to achieve a better understanding of this system. We simulate three flavors of dynamical staggered quarks with physical masses at a range of magnetic fields and temperatures, and extrapolate the results to the continuum limit. Analyzing the impact of the field on the quark condensate and the Polyakov loop, we find non-trivial spatial features that render the QCD medium qualitatively different as in the homogeneous setup, especially at temperatures around the transition. In addition, we construct leading-order chiral perturbation theory for the inhomogeneous background and compare its prediction to our lattice results at low temperature. Our findings will be useful to benchmark effective theories and low-energy models of QCD for a better description of peripheral heavy-ion collisions.
Off-central heavy-ion collisions are known to feature magnetic fields with magnitudes and characteristic gradients corresponding to the scale of the strong interactions. In this work, we employ equilibrium lattice simulations of the underlying theory, QCD, involving similar inhomogeneous magnetic field profiles to achieve a better understanding of this system. We simulate three flavors of dynamical staggered quarks with physical masses at a range of magnetic fields and temperatures, and extrapolate the results to the continuum limit. Analyzing the impact of the field on the quark condensate and the Polyakov loop, we find non-trivial spatial features that render the QCD medium qualitatively different as in the homogeneous setup, especially at temperatures around the transition. In addition, we construct leading-order chiral perturbation theory for the inhomogeneous background and compare its prediction to our lattice results at low temperature. Our findings will be useful to benchmark effective theories and low-energy models of QCD for a better description of peripheral heavy-ion collisions.
Off-central heavy-ion collisions are known to feature magnetic fields with magnitudes and characteristic gradients corresponding to the scale of the strong interactions. In this work, we employ equilibrium lattice simulations of the underlying theory, QCD, involving similar inhomogeneous magnetic field profiles to achieve a better understanding of this system. We simulate three flavors of dynamical staggered quarks with physical masses at a range of magnetic fields and temperatures, and extrapolate the results to the continuum limit. Analyzing the impact of the field on the quark condensate and the Polyakov loop, we find non-trivial spatial features that render the QCD medium qualitatively different as in the homogeneous setup, especially at temperatures around the transition. In addition, we construct leading-order chiral perturbation theory for the inhomogeneous background and compare its prediction to our lattice results at low temperature. Our findings will be useful to benchmark effective theories and low-energy models of QCD for a better description of peripheral heavy-ion collisions.
Human feline leukemia virus subgroup C receptor-related proteins 1 and 2 (FLVCR1 and 2) are members of the major facilitator superfamily1. Their dysfunction is linked to several clinical disorders, including PCARP, HSAN, and Fowler syndrome2–7. Earlier studies concluded that FLVCR1 may function as a putative heme exporter8–12, while FLVCR2 was suggested to act as a heme importer13, yet conclusive biochemical and detailed molecular evidence remained elusive for the function of both transporters14–17. Here, we show that FLVCR1 and FLVCR2 facilitate the transport of choline and ethanolamine across human plasma membranes, utilizing a concentration-driven substrate translocation process. Through structural and computational analyses, we have identified distinct conformational states of FLVCRs and unraveled the coordination chemistry underlying their substrate interactions. Within the binding pocket of both transporters, we identify fully conserved tryptophan and tyrosine residues holding a central role in the formation of cation-π interactions, essential for choline and ethanolamine selectivity. Our findings not only clarify the mechanisms of choline and ethanolamine transport by FLVCR1 and FLVCR2, enhancing our comprehension of disease-associated mutations that interfere with these vital processes, but also shed light on the conformational dynamics of these MFS-type proteins during the transport cycle.
The polarization of Λ and Λ¯ hyperons along the beam direction has been measured relative to the second and third harmonic event planes in isobar Ru+Ru and Zr+Zr collisions at √sNN = 200 GeV. This is the first experimental evidence of the hyperon polarization by the triangular flow originating from the initial density fluctuations. The amplitudes of the sine modulation for the second and third harmonic results are comparable in magnitude, increase from central to peripheral collisions, and show a mild pT dependence. The azimuthal angle dependence of the polarization follows the vorticity pattern expected due to elliptic and triangular anisotropic flow, and qualitatively disagree with most hydrodynamic model calculations based on thermal vorticity and shear induced contributions. The model results based on one of existing implementations of the shear contribution lead to a correct azimuthal angle dependence, but predict centrality and pT dependence that still disagree with experimental measurements. Thus, our results provide stringent constraints on the thermal vorticity and shear-induced contributions to hyperon polarization. Comparison to previous measurements at RHIC and the LHC for the second-order harmonic results shows little dependence on the collision system size and collision energy.
The production of K∗(892)± meson resonance is measured at midrapidity (|y|<0.5) in Pb-Pb collisions at sNN−−−√=5.02 TeV using the ALICE detector at the LHC. The resonance is reconstructed via its hadronic decay channel K∗(892)±→K0Sπ±. The transverse momentum distributions are obtained for various centrality intervals in the pT range of 0.4-16 GeV/c. The reported measurements of integrated yields, mean transverse momenta, and particle yield ratios are consistent with previous ALICE measurements for K∗(892)0. The pT-integrated yield ratio 2K∗(892)±/(K++K−) in central Pb-Pb collisions shows a significant suppression (9.3σ) relative to pp collisions. Thermal model calculations overpredict the particle yield ratio. Although both simulations consider the hadronic phase, only HRG-PCE accurately represents the measurements, whereas MUSIC+SMASH tends to overpredict them. These observations, along with the kinetic freeze-out temperatures extracted from the yields of light-flavored hadrons using the HRG-PCE model, indicate a finite hadronic phase lifetime, which increases towards central collisions. The pT-differential yield ratios 2K∗(892)±/(K++K−) and 2K∗(892)±/(π++π−) are suppressed by up to a factor of five at pT<2 GeV/c in central Pb-Pb collisions compared to pp collisions at s√= 5.02 TeV. Both particle ratios and are qualitatively consistent with expectations for rescattering effects in the hadronic phase. The nuclear modification factor shows a smooth evolution with centrality and is below unity at pT>8 GeV/c, consistent with measurements for other light-flavored hadrons. The smallest values are observed in most central collisions, indicating larger energy loss of partons traversing the dense medium.
A new, more precise measurement of the Λ hyperon lifetime is performed using a large data sample of Pb–Pb collisions at √sNN p ¼ 5.02 TeV with ALICE. The Λ and Λ¯ hyperons are reconstructed at midrapidity using their two-body weak decay channel Λ → p þ π− and Λ¯ → p¯ þ πþ. The measured value of the Λ lifetime is τΛ ¼ ½261.07 0.37ðstat:Þ 0.72ðsyst:Þ ps. The relative difference between the lifetime of Λ and Λ¯ , which represents an important test of CPT invariance in the strangeness sector, is also measured. The obtained value ðτΛ − τΛ¯Þ=τΛ ¼ 0.0013 0.0028ðstat:Þ 0.0021ðsyst:Þ is consistent with zero within the uncertainties. Both measurements of the Λ hyperon lifetime and of the relative difference between τΛ and τΛ¯ are in agreement with the corresponding world averages of the Particle Data Group and about a factor of three more precise.
First measurement of Λ+c production down to pT = 0 in pp and p-Pb collisions at √𝑠NN = 5.02 TeV
(2023)
The production of prompt +c baryons has been measured at midrapidity in the transverse momentum interval 0 < pT < 1 GeV/c for the first time, in pp and p–Pb collisions at a center-of-mass energy per nucleon-nucleon collision √sNN = 5.02 TeV. The measurement was performed in the decay channel +c → pK0S by applying new decay reconstruction techniques using a Kalman-Filter vertexing algorithm and adopting a machine-learning approach for the candidate selection. The pT -integrated +c production cross sections in both collision systems were determined and used along with the measured yields in Pb–Pb collisions to compute the pT -integrated nuclear modification factors RpPb and RAA of +c baryons, which are compared to model calculations that consider nuclear modification of the parton distribution functions. The +c /D0 baryon-to-meson yield ratio is reported for pp and p–Pb collisions. Comparisons with models that include modified hadronization processes are presented, and the implications of the results on the understanding of charm hadronization in hadronic collisions are discussed. A significant (3.7σ) modification of the mean transverse momentum of + c baryons is seen in p–Pb collisions with respect to pp collisions, while the pT -integrated +c /D0 yield ratio was found to be consistent between the two collision systems within the uncertainties.
The measurement of the production of deuterons, tritons and 3He and their antiparticles in Pb-Pb collisions at √sNN = 5.02 TeV is presented in this article. The measurements are carried out at midrapidity (y|< 0.5) as a function of collision centrality using the ALICE detector. The pT-integrated yields, the coalescence parameters and the ratios to protons and antiprotons are reported and compared with nucleosynthesis models. The comparison of these results in different collision systems at different center-of-mass collision energies reveals a suppression of nucleus production in small systems. In the Statistical Hadronisation Model framework, this can be explained by a small correlation volume where the baryon number is conserved, as already shown in previous fluctuation analyses. However, a different size of the correlation volume is required to describe the proton yields in the same data sets. The coalescence model can describe this suppression by the fact that the wave functions of the nuclei are large and the fireball size starts to become comparable and even much smaller than the actual nucleus at low multiplicities.
The knowledge of the material budget with a high precision is fundamental for measurements of direct photon production using the photon conversion method due to its direct impact on the total systematic uncertainty. Moreover, it influences many aspects of the charged-particle reconstruction performance. In this article, two procedures to determine data-driven corrections to the material-budget description in ALICE simulation software are developed. One is based on the precise knowledge of the gas composition in the Time Projection Chamber. The other is based on the robustness of the ratio between the produced number of photons and charged particles, to a large extent due to the approximate isospin symmetry in the number of produced neutral and charged pions. Both methods are applied to ALICE data allowing for a reduction of the overall material budget systematic uncertainty from 4.5% down to 2.5%. Using these methods, a locally correct material budget is also achieved. The two proposed methods are generic and can be applied to any experiment in a similar fashion.
We study equilibrium as well as out-of-equilibrium properties of the strongly interacting QGP medium under extreme conditions of high temperature T and high baryon densities or baryon chemical potentials μB within a kinetic approach. We present the thermodynamic and transport properties of the QGP close to equilibrium in the framework of effective models with Nf=3 active quark flavours such as the Polyakov extended Nambu-Jona Lasinio (PNJL) and dynamical quasiparticle model with the CEP (DQPM-CP). Considering the transport coefficients and the EoS of the QGP phase, we compare our results with various results from the literature. Furthermore, out-of equilibrium properties of the QGP medium and in particular, the effect of a μB- dependence of thermodynamic and transport properties of the QGP are studied within the Parton-Hadron-String-Dynamics (PHSD) transport approach, which covers the full evolution of the system during HICs. We find that bulk observables and flow coefficients for strange hadrons as well as for antiprotons are more sensitive to the properties of the QGP, in particular to the μB - dependence of the QGP interactions.
Presolar grain isotopic ratios as constraints to nuclear physics inputs for s-process calculations
(2023)
The isotopic abundances in presolar SiC grains of AGB origin provide important and precise constraints to those star nucleosynthesis models. By comparing the values of the s-element abundances resulting from calculations with the ones measured in these dust grains, it turns out that new measurements of weak-interaction rates in ionized plasmas, as well as of neutron-capture cross sections, are needed, especially in the region near the neutron magic numbers 50 and 82.
Results on proton and Λ flow, calculated with the UrQMD model that incorporates different realistic density dependent equations of state, are presented. It is shown that the proton and hyperon flow shows sensitivity to the equation of state and especially to the appearance of a phase transition at densities below 4n0. Even though qualitatively hyperons and protons exhibit the same beam energy dependence of the flow, the quantitative results are different. In this context it is suggested that the hyperon measurements can be used to study the density dependence of the hyperon interaction in high density QCD matter.
We introduce a novel technique that utilizes a physics-driven deep learning method to reconstruct the dense matter equation of state from neutron star observables, particularly the masses and radii. The proposed framework involves two neural networks: one to optimize the EoS using Automatic Differentiation in the unsupervised learning scheme; and a pre-trained network to solve the Tolman–Oppenheimer–Volkoff (TOV) equations. The gradient-based optimization process incorporates a Bayesian picture into the proposed framework. The reconstructed EoS is proven to be consistent with the results from conventional methods. Furthermore, the resulting tidal deformation is in agreement with the limits obtained from the gravitational wave event, GW170817.
This thesis aims to investigate the properties of hadronic matter by analyzing fluctuations of conserved charges. A transport model (SMASH) is used for these studies to achieve this. The first part of this thesis focuses on examining transport coefficients, specifically the diffusion coefficients of conserved charges and the shear viscosity. The second part investigates equal-time correlations of particle numbers in the form of cumulants. The last chapter studies different aspects of the isobar collision systems Ru and Zr.
As a first step, the hadronic medium and interactions between its constituents are introduced, and simultaneously, their impact on transport coefficients is investigated. The methodology is verified by comparing the results of SMASH with Chapman-Enskog calculations, followed by examining 3-to-1 multi-particle reactions, revealing their influence on shear viscosity and electrical diffusion. The analysis of the full hadron gas considers angle-dependent cross-sections and additional elastic cross-sections via the AQM description, showing significant impacts on transport coefficients. The dependency on the number of degrees of freedom is explored, with noticeable effects on diffusion coefficients but a smaller influence on the shear viscosity. At non-zero baryon chemical potential, the diffusion coefficients are strongly influenced, while the shear viscosity remains unaffected. Overall, the study underscores the importance of individual cross-sections and the modeling of interactions on transport coefficients.
The following chapter explores fluctuations of conserved charges, crucial for understanding phase transitions in heavy-ion collision from the quark-gluon plasma to the hadronic phase. Using SMASH, the impact of global charge conservation on particle number cumulants in subvolumes of boxes simulating infinite matter is studied. Comparisons with simpler systems highlights the influence of hadronic interactions on cumulants, especially via charge annihilation processes and the results from SMASH shows agreement with analytical calculations. Calculations at finite baryon chemical potential reveals a transition from a Poisson to Skellam distribution within the net proton cumulants. It is shown that an unfolding procedure to obtain the net baryon fluctuations from the net proton ones deviates from the actual net baryon result, particularly in larger volumes. Finally, net proton correlations at vanishing baryon chemical potential align with ALICE measurements and the net proton cumulants are unaffected by deuteron formation.
In the next step, the goal is to investigate critical fluctuations in the hadronic medium. Therefore, the hadronic system is initialized with critical equilibrium fluctuations by coupling the hadron resonance gas with the 3D Ising model. The single-particle probability distributions are derived from the principle of maximum entropy. Evolving these distributions in SMASH, their development in an expanding sphere adjusted to experimental conditions can be analyzed. It reveals resonance decay and formations as the primary source that affects the particle cumulants. Because of isospin randomization processes, critical fluctuations are better preserved in net nucleon numbers. However, for the strongest coupling investigated in this work, correlations of the critical field are still present in the final state of the evolution in the net proton fluctuations. Examining cumulant dependence on rapidity windows shows a non-monotonic trend.
In the third part, collisions involving the isobars Ru and Zr are studied at a center-of-mass energy of 200 GeV. Initially, SMASH is used to study the initial conditions to hydrodynamical simulations, emphasizing the importance of the nuclear structure of isobars on the geometry of the collision area. It is found that the deformation parameters notably influence the initial state. Correlations between nucleon-nucleon pairs on eccentricity fluctuations yield no significant effect. Subsequently, the hydrodynamic model vHLLE evolves the previously explored initial conditions and for the transition between the hydrodynamic and kinetic descriptions, the Cooper-Frye formula is used. Usage of the canonical ensemble ensures the exact conservation of the conserved charges B, Q, and S. The neutron skin effect, which changes the charge distribution within Ru nuclei, is additionally considered. Fluctuations are assessed, revealing suppression in large rapidity windows due to global charge conservation. The hadronic phase modifies fluctuations of net pions, net kaons, and net protons via annihilation processes, yet fluctuations remain unaffected by the neutron skin effect.
The equation of state (EoS) of matter at extremely high temperatures and densities is currently not fully understood, and remains a major challenge in the field of nuclear physics. Neutron stars harbor such extreme conditions and therefore serve as celestial laboratories for constraining the dense matter EoS. In this thesis, we present a novel algorithm that utilizes the idea of Bayesian analysis and the computational efficiency of neural networks to reconstruct the dense matter equation of state from mass-radius observations of neutron stars. We show that the results are compatible with those from earlier works based on conventional methods, and are in agreement with the limits on tidal deformabilities obtained from the gravitational wave event, GW170817. We also observe that the resulting squared speed of sound from the reconstructed EoS features a peak, indicating a likely convergence to the conformal limit at asymptotic densities, as expected from quantum chromodynamics. The novel algorithm can also be applied across various fields faced with computational challenges in solving inverse problems. We further examine the efficiency of deep learning methods for analyzing gravitational waves from compact binary coalescences in this thesis. In particular, we develop a deep learning classifier to segregate simulated gravitational wave data into three classes: signals from binary black hole mergers, signals from binary neutron star mergers, or white noise without any signals. A second deep learning algorithm allows for the regression of chirp mass and combined tidal deformability from simulated binary neutron star mergers. An accurate estimation of these parameters is crucial to constrain the underlying EoS. Lastly, we explore the effects of finite temperatures on the binary neutron star merger remnant from GW170817. Isentropic EoSs are used to infer the frequencies of the rigidly rotating remnant and are noted to be significantly lower compared to previous estimates from zero temperature EoSs. Overall, this thesis presents novel deep learning methods to constrain the neutron star EoS, which will prove useful in future, as more observational data is expected in the upcoming years.
We have investigated the systematic differences introduced when performing a Bayesian-inference analysis of the equation of state (EOS) of neutron stars employing either variable- or constant-likelihood functions. The former has the advantage of retaining the full information on the distributions of the measurements, making exhaustive usage of the data. The latter, on the other hand, has the advantage of a much simpler implementation and reduced computational costs. In both approaches, the EOSs have identical priors and have been built using the sound speed parameterization method so as to satisfy the constraints from X-ray and gravitational waves observations, as well as those from chiral effective theory and perturbative quantum chromodynamics. In all cases, the two approaches lead to very similar results and the 90% confidence levels essentially overlap. Some differences do appear, but in regions where the probability density is extremely small and are mostly due to the sharp cutoff on the binary tidal deformability L˜ 720 set in the constant-likelihood approach. Our analysis has also produced two additional results. First, an inverse correlation between the normalized central number density, nc,TOV/ns, and the radius of a maximally massive star, RTOV. Second, and most importantly, it has confirmed the relation between the chirp mass and the binary tidal deformability. The importance of this result is that it relates chirp, which is measured very accurately, and L˜ , which contains important information on the EOS. Hence, when chirp is measured in future detections, our relation can be used to set tight constraints on L˜ .
The amplification of magnetic fields plays an important role in explaining numerous astrophysical phenomena associated with binary neutron star mergers, such as mass ejection and the powering of short gamma-ray bursts. Magnetic fields in isolated neutron stars are often assumed to be confined to a small region near the stellar surface, while they are normally taken to fill the whole star in numerical modeling of mergers. By performing high-resolution, global, and high-order general-relativistic magnetohydrodynamic simulations, we investigate the impact of a purely crustal magnetic field and contrast it with the standard configuration consisting of a dipolar magnetic field with the same magnetic energy but filling the whole star. While the crust configurations are very effective in generating strong magnetic fields during the Kelvin–Helmholtz-instability stage, they fail to achieve the same level of magnetic-field amplification of the full-star configurations. This is due to the lack of magnetized material in the neutron-star interiors to be used for further turbulent amplification and to the surface losses of highly magnetized matter in the crust configurations. Hence, the final magnetic energies in the two configurations differ by more than 1 order of magnitude. We briefly discuss the impact of these results on astrophysical observables and how they can be employed to deduce the magnetic topology in merging binaries.
Post-merger gravitational-wave signal from neutron-star binaries: a new look at an old problem
(2023)
The spectral properties of the post-merger gravitational-wave signal from a binary of neutron stars encodes a variety of information about the features of the system and of the equation of state describing matter around and above nuclear saturation density. Characterizing the properties of such a signal is an “old” problem, which first emerged when a number of frequencies were shown to be related to the properties of the binary through “quasiuniversal” relations. Here we take a new look at this old problem by computing the properties of the signal in terms of the Weyl scalar ψ4. In this way, and using a database of more than 100 simulations, we provide the first evidence for a new instantaneous frequency, y f0 4, associated with the instant of quasi-time-symmetry in the dynamics, and which also follows a quasi-universal relation. We also derive a new quasi-universal relation for the merger frequency f h mer, which provides a description of the data that is 4 times more accurate than previous expressions while requiring fewer fitting coefficients. Finally, consistent with the findings of numerous studies before ours, and using an enlarged ensemble of binary systems, we point out that the ℓ = 2, m = 1 gravitational-wave mode could become comparable with the traditional ℓ = 2, m = 2 mode on sufficiently long timescales, with strain amplitudes in a ratio |h21|/|h22| ∼ 0.1–1 under generic orientations of the binary, which could be measured by present detectors for signals with a large signal-to-noise ratio or by third-generation detectors for generic signals should no collapse occur.
Post-merger gravitational-wave signal from neutron-star binaries: a new look at an old problem
(2023)
The spectral properties of the post-merger gravitational-wave signal from a binary of neutron stars encodes a variety of information about the features of the system and of the equation of state describing matter around and above nuclear saturation density. Characterising the properties of such a signal is an “old” problem, which first emerged when a number of frequencies were shown to be related to the properties of the binary through “quasi-universal” relations. Here we take a new look at this old problem by computing the properties of the signal in terms of the Weyl scalar ψ4. In this way, and using a database of more than 100 simulations, we provide the first evidence for a new instantaneous frequency, f ψ4 0, associated with the instant of quasi timesymmetry in the postmerger dynamics, and which also follows a quasi-universal relation. We also derive a new quasi-universal relation for the merger frequency f h mer, which provides a description of the data that is four times more accurate than previous expressions while requiring fewer fitting coefficients. Finally, consistently with the findings of numerous studies before ours, and using an enlarged ensamble of binary systems we point out that the ℓ = 2, m = 1 gravitational-wave mode could become comparable with the traditional ℓ = 2, m = 2 mode on sufficiently long timescales, with strain amplitudes in a ratio |h 21|/|h 22| ∼ 0.1 − 1 under generic orientations of the binary, which could be measured by present detectors for signals with large signal-to-noise ratio or by third-generation detectors for generic signals should no collapse occur.
A considerable effort has been dedicated recently to the construction of generic equations of state (EOSs) for matter in neutron stars. The advantage of these approaches is that they can provide model-independent information on the interior structure and global properties of neutron stars. Making use of more than 106 generic EOSs, we asses the validity of quasi-universal relations of neutron star properties for a broad range of rotation rates, from slow-rotation up to the mass-shedding limit. In this way, we are able to determine with unprecedented accuracy the quasi-universal maximum-mass ratio between rotating and nonrotating stars and reveal the existence of a new relation for the surface oblateness, i.e., the ratio between the polar and equatorial proper radii. We discuss the impact that our findings have on the imminent detection of new binary neutron-star mergers and how they can be used to set new and more stringent limits on the maximum mass of nonrotating neutron stars, as well as to improve the modelling of the X-ray emission from the surface of rotating stars.
According to the inflationary theory of cosmology, most elementary particles in the current Universe were created during a period of reheating after inflation. In this Letter, we self-consistently couple the Einstein-inflaton equations to a strongly coupled quantum field theory as described by holography. We show that this leads to an inflating universe, a reheating phase, and finally a universe dominated by the quantum field theory in thermal equilibrium.
According to the inflationary theory of cosmology, most elementary particles in the current universe were created during a period of reheating after inflation. In this work we self-consistently couple the Einstein-inflaton equations to a strongly coupled quantum field theory (QFT) as described by holography. We show that this leads to an inflating universe, a reheating phase and finally a universe dominated by the QFT in thermal equilibrium.
The core of this work is represented by the investigation of the chiral phase transition, using Monte Carlo simulations and unimproved staggered fermions, both in the weak and strong coupling regimes of Quantum Chromodynamics. Based on recent results from Monte Carlo simulations, both using unimproved staggered fermions and Wilson fermions, the chiral phase transition in the continuum and chiral limit shows compatibility with a second-order phase transition for Nf (number of flavours) in range [2:7], at zero baryon chemical potential. This achievement relies on the analytic continuation of Nf to non-integer values on the lattice, which allows to make use of extrapolation techniques to the chiral limit, where simulations are not possible. Furthermore, these results provide a resolution to the ambiguous scenario for Nf = 2 in the chiral limt. The first part of this thesis is devoted to the investigation of the chiral phase transition when a non-zero imaginary baryon chemical potential is involved, whose value corresponds to the 81% of the Roberge-Weiss one. Using the same extrapolation techniques aforementioned, the order of the chiral phase transition in the continuum and chiral limit shows compatibility with a second-order phase transition for Nf in range [2:6], highlighting a lack of dependence of the order of the chiral phase transition on the imaginary baryon chemical potential value. The second part of this thesis is about the study of the extension of the first-order chiral region in the strong coupling regime, at zero baryon chemical potential. Using Monte Carlo techniques, this can be done by investigating the Z2 boundary on a coarse lattice, whose temporal extent reads Nt = 2, and simulations are realised for Nf = 4, 8. The results in the weak coupling regime show, for $Nt = 8, 6, 4 and fixed Nf value, an inflating first-order chiral region. As in the strong coupling limit a second-order chiral phase transition is expected, the first-order chiral region has to shrink as the strong coupling regime is approached, resulting in a non-monotonic behaviour of the Z2 boundary. For Nf = 8, a critical mass on the Z2 boundary has been obtained, confirming the expected non-monotonic behaviour. For Nf = 4 the results do not provide a unique conclusion: Either a Z2 boundary at extremely low bare quark mass or a second-order chiral phase transition in the O(2) universality class in the chiral limit can take place. In addition to the two main topics, the performances of the second-order minimum norm integrator (2MN) and the fourth-order minimum norm integrator (4MN) have been compared, after implementing the 4MN one in the CL2QCD code used to realise our simulations. The 2MN integrator had already been implemented in the code since the first version was released. The two integrators belong to the class of symplectic integrators and represent an essential component of the RHMC algorithm, involved in our investigation. This step is extremely important, in order to guarantee the best quality when collecting data from simulations, and the results of the comparison suggested to favor the 2MN integrator, for both the topics.
In the framework of the LHC Injectors Upgrade Project (LIU), the CERN Proton Synchrotron Booster (PSB) went through major upgrades resulting in new effects to study, challenges to overcome and new parameter regimes to explore. To assess the achievable beam brightness limit of the machine, a series of experimental and computational studies in the transverse planes were performed. In particular, the new injection scheme induces optics perturbations that are strongly enhanced near the half-integer resonance. In this thesis, methods for dynamically measuring and correcting these perturbations and their impact on the beam performance will be presented. Additionally, the quality of the transverse beam distributions and strategies for improvement will be addressed. Finally, the space charge effects when dynamically crossing the half-integer resonance will be characterized. The results of these studies and their broader significance beyond the PSB will be discussed.
This thesis provides a detailed derivation of dissipative spin hydrodynamics from quantum field theory for systems composed of spin-0, spin-1/2, or spin-1 particles.
The Wigner function formalism is introduced for quantum fields in the respective representations of the Poincaré group, and the conserved currents, i.e., the energy-momentum tensor and the total angular momentum tensor, in various so-called pseudogauges are derived. An expansion around the semiclassical limit in powers of the Planck constant is performed.
Subsequently, kinetic equations are obtained for binary elastic scattering, using both the de Groot-van Leeuwen-van Weert and Kadanoff-Baym method, with the latter retaining the effect of quantum statistics. The resulting collision term features both local and nonlocal contributions, with the latter providing a relaxation mechanism for the spin degrees of freedom of the quasiparticles. The local-equilibrium distribution function is derived from the requirement that the local part of the collision term vanishes.
From quantum kinetic theory, dissipative spin hydrodynamics is then constructed via the method of moments, extended to particles with spin. The system of moment equations is closed via the Inverse-Reynolds Dominance (IReD) approach, resulting in a set of equations of motion describing the evolution of both ideal and dissipative degrees of freedom. The application to polarization phenomena relevant to heavy-ion collisions is discussed.
Substantial progress in the field of neuroscience has been made from anaesthetized preparations. Ketamine is one of the most used drugs in electrophysiology studies, but how ketamine affects neuronal responses is poorly understood. Here, we used in vivo electrophysiology and computational modelling to study how the auditory cortex of bats responds to vocalisations under anaesthesia and in wakefulness. In wakefulness, acoustic context increases neuronal discrimination of natural sounds. Neuron models predicted that ketamine affects the contextual discrimination of sounds regardless of the type of context heard by the animals (echolocation or communication sounds). However, empirical evidence showed that the predicted effect of ketamine occurs only if the acoustic context consists of low-pitched sounds (e.g., communication calls in bats). Using the empirical data, we updated the naïve models to show that differential effects of ketamine on cortical responses can be mediated by unbalanced changes in the firing rate of feedforward inputs to cortex, and changes in the depression of thalamo-cortical synaptic receptors. Combined, our findings obtained in vivo and in silico reveal the effects and mechanisms by which ketamine affects cortical responses to vocalisations.
Hadron lists based on experimental studies summarized by the Particle Data Group (PDG) are a crucial input for the equation of state and thermal models used in the study of strongly-interacting matter produced in heavy-ion collisions. Modeling of these strongly-interacting systems is carried out via hydrodynamical simulations, which are followed by hadronic transport codes that also require a hadronic list as input. To remain consistent throughout the different stages of modeling of a heavy-ion collision, the same hadron list with its corresponding decays must be used at each step. It has been shown that even the most uncertain states listed in the PDG from 2016 are required to reproduce partial pressures and susceptibilities from Lattice Quantum Chromodynamics with the hadronic list known as the PDG2016+. Here, we update the hadronic list for use in heavy-ion collision modeling by including the latest experimental information for all states listed in the Particle Data Booklet in 2021. We then compare our new list, called PDG2021+, to Lattice Quantum Chromodynamics results and find that it achieves even better agreement with the first principles calculations than the PDG2016+ list. Furthermore, we develop a novel scheme based on intermediate decay channels that allows for only binary decays, such that PDG2021+ will be compatible with the hadronic transport framework SMASH. Finally, we use these results to make comparisons to experimental data and discuss the impact on particle yields and spectra.
DNA binding redistributes activation domain ensemble and accessibility in pioneer factor Sox2
(2023)
More than 1600 human transcription factors orchestrate the transcriptional machinery to control gene expression and cell fate. Their function is conveyed through intrinsically disordered regions (IDRs) containing activation or repression domains but lacking quantitative structural ensemble models prevents their mechanistic decoding. Here we integrate single-molecule FRET and NMR spectroscopy with molecular simulations showing that DNA binding can lead to complex changes in the IDR ensemble and accessibility. The C-terminal IDR of pioneer factor Sox2 is highly disordered but its conformational dynamics are guided by weak and dynamic charge interactions with the folded DNA binding domain. Both DNA and nucleosome binding induce major rearrangements in the IDR ensemble without affecting DNA binding affinity. Remarkably, interdomain interactions are redistributed in complex with DNA leading to variable exposure of two activation domains critical for transcription. Charged intramolecular interactions allowing for dynamic redistributions may be common in transcription factors and necessary for sensitive tuning of structural ensembles.
We show examples of the impact of the Maxwellian averaged capture cross sections determined at n_TOF over the past 20 years on AGB stellar nucleosynthesis models. In particular, we developed an automated procedure to derive MACSs from evaluated data libraries, which are subsequently used as input to stellar models computed by means of the FuNS code. In this contribution, we present a number of s-process abundances obtained using different data libraries as input to stellar models, with a focus on the role of n_TOF data.
Subensemble is a type of statistical ensemble which is the generalization of grand canonical and canonical ensembles. The subensemble acceptance method (SAM) provides general formulas to correct the cumulants of distributions in heavy-ion collisions for the global conservation of all QCD charges. The method is applicable for an arbitrary equation of state and sufficiently large systems, such as those created in central collisions of heavy ions. The new fluctuation measures insensitive to global conservation effects are presented. The main results are illustrated in the hadron resonance gas and van der Waals fluid frameworks.