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The Transition Radiation Detector (TRD) was designed and built to enhance the capabilities of the ALICE detector at the Large Hadron Collider (LHC). While aimed at providing electron identification and triggering, the TRD also contributes significantly to the track reconstruction and calibration in the central barrel of ALICE. In this paper the design, construction, operation, and performance of this detector are discussed. A pion rejection factor of up to 410 is achieved at a momentum of 1 GeV/c in p-Pb collisions and the resolution at high transverse momentum improves by about 40% when including the TRD information in track reconstruction. The triggering capability is demonstrated both for jet, light nuclei, and electron selection.
The Transition Radiation Detector (TRD) was designed and built to enhance the capabilities of the ALICE detector at the Large Hadron Collider (LHC). While aimed at providing electron identification and triggering, the TRD also contributes significantly to the track reconstruction and calibration in the central barrel of ALICE. In this paper the design, construction, operation, and performance of this detector are discussed. A pion rejection factor of up to 410 is achieved at a momentum of 1 GeV/c in p-Pb collisions and the resolution at high transverse momentum improves by about 40% when including the TRD information in track reconstruction. The triggering capability is demonstrated both for jet, light nuclei, and electron selection.
The Transition Radiation Detector (TRD) was designed and built to enhance the capabilities of the ALICE detector at the Large Hadron Collider (LHC). While aimed at providing electron identification and triggering, the TRD also contributes significantly to the track reconstruction and calibration in the central barrel of ALICE. In this paper the design, construction, operation, and performance of this detector are discussed. A pion rejection factor of up to 410 is achieved at a momentum of 1 GeV/c in p–Pb collisions and the resolution at high transverse momentum improves by about 40% when including the TRD information in track reconstruction. The triggering capability is demonstrated both for jet, light nuclei, and electron selection.
The first measurement of ϕ-meson production in p-Pb collisions at a nucleon-nucleon centre-of-mass energy sNN−−−√ = 5.02 TeV has been performed with the ALICE apparatus at the LHC. The ϕ-mesons have been identified in the dimuon decay channel in the transverse momentum (pT) range 1<pT<7 GeV/c, both in the p-going (2.03<y<3.53) and the Pb-going (−4.46<y<−2.96) directions, where y stands for the rapidity in the nucleon-nucleon centre-of-mass. Differential cross sections as a function of transverse momentum and rapidity are presented. The forward-backward asymmetry for ϕ-meson production is measured for 2.96<|y|<3.53, resulting in a factor ∼0.5 with no significant pT dependence within the uncertainties. The pT dependence of the ϕ nuclear modification factor RpPb exhibits an enhancement up to a factor 1.6 at pT = 3-4 GeV/c in the Pb-going direction. The pT dependence of the ϕ-meson cross section in pp collisions at s√ = 2.76 TeV, which is used to determine a reference for the p-Pb results, is also presented here for 1<pT<5 GeV/c and 2.5<y<4.
We report on results obtained with the Event Shape Engineering technique applied to Pb-Pb collisions at sNN−−−√=2.76 TeV. By selecting events in the same centrality interval, but with very different average flow, different initial state conditions can be studied. We find the effect of the event-shape selection on the elliptic flow coefficient v2 to be almost independent of transverse momentum pT, as expected if this effect is due to fluctuations in the initial geometry of the system. Charged hadron, pion, kaon, and proton transverse momentum distributions are found to be harder in events with higher-than-average elliptic flow, indicating an interplay between radial and elliptic flow.
Transverse momentum (pT) spectra of pions, kaons, and protons up to pT=20 GeV/c have been measured in Pb-Pb collisions at sNN−−−√=2.76 TeV using the ALICE detector for six different centrality classes covering 0-80%. The proton-to-pion and the kaon-to-pion ratios both show a distinct peak at pT≈3 GeV/c in central Pb-Pb collisions that decreases towards more peripheral collisions. For pT>10 GeV/c, the nuclear modification factor is found to be the same for all three particle species in each centrality interval within systematic uncertainties of 10-20%. This suggests there is no direct interplay between the energy loss in the medium and the particle species composition in the hard core of the quenched jet. For pT<10 GeV/c, the data provide important constraints for models aimed at describing the transition from soft to hard physics.
Als am späten Abend des 25. Juni 1935 die Lichter gelöscht und die Türen des Pariser Versammlungsgebäudes der Mutualité geschlossen sind, ist der Schriftstellerkongreß zur Verteidigung der Kultur nicht Vergangenheit. Um seine Bedeutung zu begreifen wie um zu verstehen, warum sie sich so schnell verflüchtigen konnte, genügt die Betrachtung des Ereignisses nicht. Wie ist er von denen aufgenommen worden, die ihn nicht aktiv gestaltet haben oder am Rande bleiben mußten? Wie haben die Akteure ihr Engagement und ihre Divergenzen fortgesetzt? Was hat die Schriftstellervereinigung, die in Paris gegründet worden ist, getan und was ist aus ihr geworden bis zum Beginn jenes Krieges, der aus heutiger Sicht das Jahrzehnt so weitgehend bestimmt und den - bei allem, was auf ihn hindeutet - die Kongreßteilnehmer noch zu verhindern, nicht leben zu müssen hoffen? Auf diese drei Fragen sollen im folgenden Antworten versucht werden.
Zwei Überlegungen haben die Wahl des Gegenstandes bestimmt. Die erste ist pragmatisch-systematischer Art. Als die Denkschrift Geisteswissenschaften heute 1991 den von ihr ins Auge gefassten Wissenschaften "als Kulturwissenschaften eine neue Perspektive" vorzeichnete und dazu "Kultur" als "Inbegriff aller menschlichen Arbeits- und Lebensformen" charakterisierte, hat sie zumindest hierzulande eine Welle zuvor ungesehener transdisziplinärer Gegenstandsbestimmungen, Forschungsparadigmen, Projekte und Professurdenominationen ausgelöst. Dies alles hat entschieden über frühere Rahmen wie Cultural Studies, Sciences de la culture oder (für in Deutschland so genannte 'Fremdphilologien') Landeskunde hinausgegriffen und hinausgeführt. Entsprechend den vielfältigen Aspekten, die 'Kultur' zu bieten vermag, stehen deren Erkundung tendenziell kaum endliche Räume offen. Neue und bedeutende Erkenntnisse über jeweils besondere Ordnungen "des geselligen Verkehrs der Menschen" und die darin wirkenden "Absichten" wurden und werden erarbeitet. Die Folge von 'turns', die nicht selten auf ernste Erkenntnis zielen, mit deren Propagierung aber auch Aufmerksamkeit, Netzwerke und Drittmittel für einzelne Bereiche dieser Arbeit geschaffen werden sollen, ist beeindruckend. Nicht alle Beteiligten möchten andererseits die aus dem 19. Jahrhundert hergebrachte Organisation der Wissenschaft in voneinander getrennten Disziplinen überhaupt in Frage gestellt sehen - seien es deren Vertreter selbst, die das Bewährte als zu Bewahrendes betrachten, seien es die Administratoren nach älteren Mustern gewirkter Universitäten, die Finanz- und Stellenpläne sparversessen weiter oder wieder so zu stricken suchen wie bisher. Extremistische Tendenzen entweder zum Aufgeben der Disziplinen zugunsten kleinteiliger Gegenstandsbereiche oder zur Rücknahme der kulturwissenschaftlichen Öffnung, zum Beispiel zugunsten einer erneuten Rephilologisierung, sind in Wissenschaftsgremien und Wissenschaftsverwaltungen unverkennbar.
Outcomes of SARS-CoV-2 infections in patients with neurodegenerative diseases in the LEOSS cohort
(2021)
The impact of preexisting neurodegenerative diseases on superimposed SARS-CoV-2 infections remains controversial. Here we examined the course and outcome of SARS-CoV-2 infections in patients affected by Parkinson's disease (PD) or dementia compared to matched controls without neurodegenerative diseases in the LEOSS (Lean European Open Survey on SARS-CoV-2-infected patients) cohort, a large-scale prospective multicenter cohort study...
Background & Aims: Phosphodiesterase‐5 inhibitors (PDE‐5‐I) are used for treatment of erectile dysfunction (ED), which is common in patients with cirrhosis. They may improve portal hypertension (PH), but contradictory data on efficacy and side‐effects have been reported. Non‐selective beta blockers (NSBB) reduce portal pressure, but might aggravate ED. Thus, we evaluated the combination of PDE‐5‐I with NSBB and its impact on PH and ED in experimental cirrhosis.
Methods: ED was assessed in cirrhotic patients (n = 86) using standardized questionnaire. Experimental cirrhosis was induced by bile‐duct‐ligation or carbon‐tetrachloride intoxication in rats. Corpus cavernosum pressure – a surrogate of ED ‐, as well as systemic and portal haemodynamics, were measured in vivo and in situ after acute administration of udenafil alone or in combination with propranolol. mRNA and protein levels of PDE‐5 signalling were analysed using PCR and western Blot.
Results: ED in humans was related to severity of liver disease and to NSBB treatment. PDE‐5 was mainly expressed in hepatic stellate cells and upregulated in human and experimental cirrhosis. Propranolol reduced corpus cavernosum pressure in cirrhotic rats and it was restored by udenafil. Even though udenafil treatment improved PH, it led to a reduction of mean arterial pressure. The combination of udenafil and propranolol reduced portal pressure and hepatic resistance without systemic side‐effects.
Conclusions: ED is common with advanced cirrhosis and concomitant NSBB treatment. The combination of PDE‐5‐I and NSBB improves ED and PH in experimental cirrhosis.
A new method of measuring quality factors in cavities is presented. This method is well suited to measure quality factors in undamped cavities as well as in heavily damped cavities, and in addition this method provides a possibility of separating modes and measuring quality factors especially in cases of overlapping modes. Measurements have been carried out on HOM-damped cavities for the DESY/THD linear collider project. Results are presented.
Damping cells for the higher order modes are necessary for the S-band linear collider to minimize BBU (Beam-Break-Up). The construction of the damper cells has to take into account the different field geometries of the higher order modes. So two different types of dampers have been designed: a wall slotted an an iris slotted cell. In order to optimize the two types of damping cells with respect to damping strength, impedance matching between coupling system and waveguide dampers and between damping cell and undamped cells and the tuning system, damping cells of both types have been built and examinated.
A new method for the determination of S-matrices of devices in multimoded waveguides and first experimental experiences are presented. The theoretical foundations are given. The scattering matrix of a TESLA copper cavity at a frequency above the cut-off of the second waveguide mode has been measured.
Due to the additional need of very short bunches for the FEL operation with the TESLA-machine strong wakefield effects are expected. One third of the total wakefield energy per bunch is radiated into the frequency region above the energy gap of Cooper pairs in superconducting niobium. The energy of the cooper pairs in superconducting niobium at 2 K corresponds to a frequency of 700 GHz. An analytical and experimental estimation for the overall energy loss of the FEL bunch above energy gap is presented. The analytical method is based on a study from R. B. Palmer [1]. The results of the wakefield estimations are used to calculate possible quality factor reduction of the TESLA cavities during FEL operation. Results are presented.
The operation of a Free Electron Laser (FEL) in the ultraviolet or in the X-ray regime requires the acceleration of electron bunches with an rms length of 25 to 50 mikrometer. The wakefields generated by these sub picosecond bunches extend into the frequency range well beyond the threshold for Cooper pair breakup (about 750 GHz) in superconducting niobium at 2 K. It is shown, that the superconducting cavities can indeed be operated with 25 mikrometer bunches without suffering a breakdown of superconductivity (quench), however at the price of a reduced quality factor and an increased heat transfer to the superfluid helium bath. This was first shown by wakefield calculations based on the diffraction model [1]. In the meantime a more conventional method of computing wake fields in the time domain by numerical methods was developed and used for the wakefield calculations [2]. Both methods lead to comparable results: the operation of TESLA with 25 mikrometer bunches is possible but leads to an additional heat load due to the higher order modes (HOMs). Therefore HOM dampers for these high frequencies are under construction [3]. These dampers are located in the beam pipes between the 9-cell cavities. So it is of interest, if there are trapped modes in the cavity due to closed photon orbits. In this paper we investigate the existence of trapped modes and the distribution of heat load over the surface of the TESLA cavity by numerical photon tracking.
The effect of a single HOM-damper cell within a channel of undamped cells is described theoretically using an equivalent circuit model. From this a simple equation can be derived which relates the Q-value of the single damping-cell, the bandwidth of the passband under consideration, and the additional phase shift which is introduced by the damper cell to provide energy flow into the damper cell. This equation immediately shows the limitations of such single cell damping systems. Comparisons with experimental results are shown.
Mode propagation in an iris type accelerator section loaded with single heavily HOM-damped cells
(1994)
The wakefield effects in accelerator sections for future linear colliders will be reduced either by damping by detuning or by a combination of both. For the DESY/THD linac [1] it is forseen to employ heavily HOM-damped cells to provide a strong coupling to the TE/TM11-dipole passband as well as to the TM/TE11-dipole passband. For our experiments we have used wall-slotted damping cells. This leads to several problems concerning the propagation of fundamental and HOM-modes. Experimental investigations have been done. Results are presented.
A new method for measuring quality factors in cavities is presented. This method is capable of measuring Q-factors in heavily damped as well as in undamped cavities. In addition, the possibility of separating overlapping modes and measuring their Q-factors is provided. Measurements on HOM (higher order mode) damped cavities for the DESY/THD linear collider project are presented
Einer vor allem nach 1989 verbreiteten Meinung zufolge bildete sich 1945 "ein tragischer Zwiespalt zwischen den Ereignissen und der Geschichte der Ideen, der die Welt im Dunkel lässt und über wenigstens dreißig Jahre Folgen haben wird". Denn "die Menschen, die sich mit den Aufgaben des Geistes befassen und deren Berufung es ist aufzuklären, Verbindungen zwischen den im Unklaren gebliebenen Tatsachen aufzuzeigen, Spiritualisten, Christen, klassische Liberale, Existentialisten, Marxisten sind keineswegs darauf vorbereitet, die Ereignisse zu erklären [...]: ihre allzu begrenzten, ihrer selbst kaum bewussten Traditionen lenken sie nicht nur von den auszuarbeitenden Analysen, sondern von den Tatsachen selbst ab."
Weshalb verfehlten sie ihre Berufung? Nach "dem schrecklichsten Rückschritt der Menschheit", der durchlebt worden war, sei "ein Befragen der Demokratie und des Christentums" erforderlich gewesen. Stattdessen treffe man nach dem Zweiten Weltkrieg allzu oft auf die "Faszination des Kommunismus" und auf "das Verknüpfen der Auffassung von Modernisierung mit denen des Fortschritts und der Perfektibilität". Die hier zitierte Überlegung führt hin zu der Feststellung einer "'französischen Krise der Aufklärung', einer 'intellektuellen Verwirrung' in der unmittelbaren Nachkriegszeit, die weder 1945 noch seitdem bewältigt worden ist".
Dieser Beschreibung zufolge begriffen die damaligen Intellektuellen in ihrer allzu großen Mehrheit nichts oder fast nichts von dem, was sich ereignete. Und noch wer sich heute mit "fortschrittlicher" Kultur und ihrer Geschichte beschäftige, liefe Gefahr, die Blindheit fortzusetzen, die sich in jener Zeit offenbart haben soll.