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Stock, Reinhard ; Fischer, Tatjana ; Aßmus, Katharina ; Zöller, Nadja Nicole ; Ackermann, Hanns ; Kaufmann, Roland ; Meissner, Markus ; Valesky, Eva Maria
Background: Current literature is inconsistent regarding the risk of severe side effects using accelerated induction protocols in Hymenoptera venom immunotherapy (VIT). In addition, several data indicate the influence of purity grade of venom preparation on tolerability. We evaluated the safety and tolerability of ultra-rush and rush build-up protocols using purified and non-purified venom preparations. Methods: Retrospective single-center study of 581 VIT inductions (325 ultra-rush and 256 rush protocols) from 2005 to 2018 in 559 patients with bee and vespid venom allergy using aqueous purified (ALK SQ®) for ultra-rush protocol and aqueous non-purified (ALK Reless®) venom preparations for rush protocol. Results: Urticaria (8% vs. 3.1%, p = 0,013) and dose reductions (4.3% vs. 1.2%, p = 0,026) were significantly more frequent in the ultra-rush group. Overall rate of moderate-to-severe side effects (anaphylaxis ≥grade 2 according to Ring and Meβmer) was low and did not differ significantly between protocols (p = 0.105). Severe events (grade 4 anaphylaxis) were not reported. Discontinuation rate was very low in both cohorts (0.6% vs 1.2%). The higher purity grade of venom preparations in the ultra-rush cohort did not improve tolerability. The bee venom group showed a non-significant trend towards higher incidence of mild reactions (urticaria), resulting in more frequent dose reductions and antiallergic therapy. Conclusion: Rush and ultra-rush protocols show an excellent safety profile with only infrequent and mild anaphylactic reactions in bee and vespid venom allergy. Ultra-rush immunotherapy reduces the duration of the inpatient build-up phase setting and thus is viewed by the authors as preferred treatment in Hymenoptera venom allergic patients.
In high multiplicity nucleus-nucleus collisions baryon-antibaryon annihilation and regeneration occur during the final hadronic expansion phase, thus distorting the initial equilibrium multiplicity ratios. We quantify the modifications employing the hybrid UrQMD transport model and apply them to the grand canonical partition functions of the Statistical Hadronization Model(SHM). We analyze minimum bias and central Pb+Pb collision data at SPS and LHC energy. We explain the Pion to Proton ratio puzzle. We also reproduce the deuteron to proton ratio at LHC energy by the SHM, and by UrQMD after attaching a phase space coalescence process. We discuss the resulting (T,μB) diagram.
Stock, Reinhard ; Becattini, Francesco ; Bleicher, Marcus ; Kollegger, Thorsten ; Schuster, Tim ; Steinheimer-Froschauer, Jan
We analyze hadrochemical freeze-out in central Pb+Pb collisions at CERN SPS and LHC energies. Employing the UrQMD hybrid transport model we study the effects of the final hadron/resonance expansion phase on the hadron multiplicities established at hadronization. The bulk meson yields freeze out directly at hadronization whereas the baryon-antibaryon sector is subject to significant alterations, due to annihilation and regeneration processes. We quantify the latter changes by survival factors for each species which are applied to modify the statistical model predictions for the data. The modified SM analysis recovers the hadronization points, which coincide with the recent lattice QCD predictions of the parton-hadron transition line at finite baryochemical potential.
Seyboth, Peter ; Kniege, Stefan ; Antičić, Tome ; Barna, Daniel ; Bartke, Jerzy ; Barton, Robert Allan ; Betev, Latchezar ; Białkowska, Helena ; Billmeier, Anja ; Blume, Christoph ; Blyth, Charles O. ; Boimska, Bożena ; Botje, Michiel ; Bracinik, Juraj ; Bramm, Roland ; Brun, René ; Bunčić, Predrag ; Cerny, Vladimír ; Chvala, Ondrej ; Cramer, John G. ; Csató, Péter ; Dinkelaker, Peter ; Eckardt, Volker ; Filip, Peter ; Fischer, Hans Gerhard ; Fodor, Zoltán ; Foka, Panagiota ; Freund, Peter ; Friese, Volker ; Gál, József ; Gaździcki, Marek ; Georgopoulos, George ; Gładysz-Dziaduś, Ewa ; Hegyi, Sándor ; Höhne, Claudia ; Jones, Peter Graham ; Kadija, Krešo ; Karev, Alexandre ; Kolesnikov, Vadim I. ; Kollegger, Thorsten ; Kowalski, Marek ; Kraus, Ingrid ; Kreps, Michal ; Leeuwen, Marco van ; Lévai, Péter ; Malakhov, Aleksandr I. ; Markert, Christina ; Mayes, Bill W. ; Melkumov, Georgy L. ; Mischke, André ; Molnár, József ; Nelson, John M. ; Pálla, Gabriella ; Panagiotou, Apostolos D. ; Perl, Katarzyna ; Petridis, Athanasios ; Pikna, Miroslav ; Pinsky, Lawrence ; Pühlhofer, Falk ; Reid, Jeffrey G. ; Renfordt, Rainer Arno Ernst ; Retyk, Waldemar ; Roland, Christof ; Roland, Gunther ; Rybicki, Andrzej ; Sandoval, Andres ; Sann, Hans ; Schmitz, Norbert ; Siklér, Ferenc ; Sitar, Branislav ; Skrzypczak, Ewa ; Squier, Gordon Thomas Anderson ; Stock, Reinhard ; Ströbele, Herbert ; Šuša, Tatjana ; Szentpétery, Imre ; Sziklai, János ; Trainor, Thomas A. ; Varga, Dezsö ; Vassiliou, Maria ; Veres, Gábor I. ; Vesztergombi, György ; Vranić, Danilo ; Wenig, Siegfried ; Wetzler, Alexander Albert ; Yoo, In-Kwon ; Zaranek, Jacek ; Zimányi, József
Experiment NA49 at the Cern SPS uses a large acceptance detector for a systematic study of particle yields and correlations in nucleus-nucleus, nucleon-nucleus and nucleon-nucleon collisions. Preliminary results for Pb+Pb collisions at 40, 80 and 158 A*GeV beam energy are shown and compared to measurements at lower and higher energies.
Rybczyński, Maciej ; Alt, Christopher ; Antičić, Tome ; Baatar, B. ; Barna, Daniel ; Bartke, Jerzy ; Betev, Latchezar ; Białkowska, Helena ; Billmeier, Anja ; Blume, Christoph ; Boimska, Bożena ; Botje, Michiel ; Bracinik, Juraj ; Bramm, Roland ; Brun, René ; Bunčić, Predrag ; Cerny, Vladimír ; Christakoglou, Panagiotis ; Chvala, Ondrej ; Cramer, John G. ; Csató, Péter ; Darmenov, Nikolay ; Dimitrov, Anton ; Dinkelaker, Peter ; Eckardt, Volker ; Farantatos, Gerassimos ; Flierl, Dominik Bernhard ; Fodor, Zoltán ; Foka, Panagiota ; Freund, Peter ; Friese, Volker ; Gál, József ; Gaździcki, Marek ; Georgopoulos, George ; Gładysz-Dziaduś, Ewa ; Grebieszkow, Katarzyna ; Hegyi, Sándor ; Höhne, Claudia ; Kadija, Krešo ; Karev, Alexandre ; Kliemant, Michael ; Kniege, Stefan ; Kolesnikov, Vadim I. ; Kollegger, Thorsten ; Kornas, Ewelina ; Korus, Robert ; Kowalski, Marek ; Kraus, Ingrid ; Kreps, Michal ; Leeuwen, Marco van ; Lévai, Péter ; Litov, Leandr ; Lungwitz, Benjamin ; Makariev, Martin ; Malakhov, Aleksandr I. ; Markert, Christina ; Mateev, Matej D. ; Mayes, Bill W. ; Melkumov, Georgy L. ; Meurer, Christine ; Mischke, André ; Mitrovski, Michael Kosta ; Molnár, József ; Mrówczyński, Stanislaw ; Pálla, Gabriella ; Panagiotou, Apostolos D. ; Panayotov, Dobromir ; Petridis, Athanasios ; Pikna, Miroslav ; Pinsky, Lawrence ; Pühlhofer, Falk ; Reid, Jeffrey G. ; Renfordt, Rainer Arno Ernst ; Richard, Agnes Carol Joanna ; Roland, Christof ; Roland, Gunther ; Rybicki, Andrzej ; Sandoval, Andres ; Sann, Hans ; Schmitz, Norbert ; Seyboth, Peter ; Siklér, Ferenc ; Sitar, Branislav ; Skrzypczak, Ewa ; Stefanek, Grzegorz ; Stock, Reinhard ; Ströbele, Herbert ; Susa, Tatjana ; Szentpétery, Imre ; Sziklai, János ; Trainor, Thomas A. ; Trubnikov, Victor ; Varga, Dezsö ; Vassiliou, Maria ; Veres, Gábor I. ; Vesztergombi, György ; Vranić, Danilo ; Wetzler, Alexander Albert ; Włodarczyk, Zbigniew ; Yoo, In-Kwon ; Zaranek, Jacek ; Zimányi, József
System size dependence of multiplicity fluctuations of charged particles produced in nuclear collisions at 158 A GeV was studied in the NA49 CERN experiment. Results indicate a non-monotonic dependence of the scaled variance of the multiplicity distribution with a maximum for semi-peripheral Pb+Pb interactions with number of projectile participants of about 35. This effect is not observed in a string-hadronic model of nuclear collision HIJING.
Event-by-event fluctuations of particle ratios in central Pb + Pb collisions at 20 to 158 AGeV
(2004)
Roland, Christof ; Alt, Christopher ; Antičić, Tome ; Baatar, B. ; Barna, Daniel ; Bartke, Jerzy ; Betev, Latchezar ; Białkowska, Helena ; Billmeier, Anja ; Blume, Christoph ; Boimska, Bożena ; Botje, Michiel ; Bracinik, Juraj ; Bramm, Roland ; Brun, René ; Bunčić, Predrag ; Cerny, Vladimír ; Christakoglou, Panagiotis ; Chvala, Ondrej ; Cramer, John G. ; Csató, Péter ; Darmenov, Nikolay ; Dimitrov, Anton ; Dinkelaker, Peter ; Eckardt, Volker ; Farantatos, Gerassimos ; Flierl, Dominik Bernhard ; Fodor, Zoltán ; Foka, Panagiota ; Freund, Peter ; Friese, Volker ; Gál, József ; Gaździcki, Marek ; Georgopoulos, George ; Gładysz, Ewa ; Grebieszkow, Katarzyna ; Hegyi, Sándor ; Höhne, Claudia ; Kadija, Krešo ; Karev, Alexandre ; Kliemant, Michael ; Kniege, Stefan ; Kolesnikov, Vadim I. ; Kollegger, Thorsten ; Kornaś, Ewelina ; Korus, Robert ; Kowalski, Marek ; Kraus, Ingrid ; Kreps, Michal ; Leeuwen, Marco van ; Lévai, Péter ; Litov, Leandr ; Lungwitz, Benjamin ; Makariev, Martin ; Malakhov, Aleksandr I. ; Markert, Christina ; Mateev, Matej D. ; Mayes, Bill W. ; Melkumov, Georgy L. ; Meurer, Christine ; Mischke, André ; Mitrovski, Michael Kosta ; Molnár, József ; Mrówczyński, Stanislaw ; Pálla, Gabriella ; Panagiotou, Apostolos D. ; Panayotov, Dobromir ; Petridis, Athanasios ; Pikna, Miroslav ; Pinsky, Lawrence ; Pühlhofer, Falk ; Reid, Jeffrey G. ; Renfordt, Rainer Arno Ernst ; Roland, Gunther ; Richard, Agnes Carol Joanna ; Rybczyński, Maciej ; Rybicki, Andrzej ; Sandoval, Andres ; Sann, Hans ; Schmitz, Norbert ; Seyboth, Peter ; Siklér, Ferenc ; Sitar, Branislav ; Skrzypczak, Ewa ; Stefanek, Grzegorz ; Stock, Reinhard ; Ströbele, Herbert ; Šuša, Tatjana ; Szentpétery, Imre ; Sziklai, János ; Trainor, Thomas A. ; Varga, Dezsö ; Vassiliou, Maria ; Veres, Gábor I. ; Vesztergombi, György ; Vranić, Danilo ; Wetzler, Alexander Albert ; Włodarczyk, Zbigniew ; Yoo, In-Kwon ; Zaranek, Jacek ; Zimányi, József
In the vicinity of the QCD phase transition, critical fluctuations have been predicted to lead to non-statistical fluctuations of particle ratios, depending on the nature of the phase transition. Recent results of the NA49 energy scan program show a sharp maximum of the ratio of K+ to Pi+ yields in central Pb+Pb collisions at beam energies of 20-30 AGeV. This observation has been interpreted as an indication of a phase transition at low SPS energies. We present first results on event-by-event fluctuations of the kaon to pion and proton to pion ratios at beam energies close to this maximum.
Odyniec, Grazyna Janina ; Afanasiev, Sergey V. ; Alber, Thomas ; Appelshäuser, Harald ; Bächler, Joachim ; Bailey, Stephen John ; Barnby, Lee Stuart ; Bartke, Jerzy ; Białkowska, Helena ; Blyth, Charles O. ; Bock, Rudolf ; Bormann, Christian ; Brady, Franklin Paul ; Brockmann, Robert ; Buncic, Nenad ; Bunčić, Predrag ; Caines, Helen Louise ; Cebra, Daniel A. ; Chan, P. ; Cooper, Glenn E. ; Cramer, John G. ; Cramer, Pauline B. ; Csató, Péter ; Dietz, Oliver ; Dunn, Jason ; Eckardt, Volker ; Eckhardt, Frank ; Ferguson, M. I. ; Fischer, Hans Gerhard ; Flierl, Dominik Bernhard ; Fodor, Zoltán ; Foka, Panagiota ; Freund, Peter ; Friese, Volker ; Fuchs, M. ; Gabler, Frank ; Gál, József ; Gaździcki, Marek ; Gładysz-Dziaduś, Ewa ; Grebieszkow, Jaroslaw ; Günther, Jörg ; Harris, John W. ; Hegyi, Sándor ; Henkel, Torsten ; Hill, L. A. ; Huang, Isaac ; Howe, Mark A. ; Hümmler, Holm Gero ; Igo, George J. ; Irmscher, Detlef ; Jacobs, Peter Martin ; Jones, Peter Graham ; Kadija, Krešo ; Kolesnikov, Vadim I. ; Konashenok, Anton ; Kowalski, Marek ; Lasiuk, Brian ; Lévai, Péter ; Malakhov, Aleksandr I. ; Margetis, Spyridon ; Markert, Christina ; Melkumov, Georgy L. ; Mock, Andreas ; Molnár, József ; Nelson, John M. ; Pálla, Gabriella ; Panagiotou, Apostolos D. ; Petridis, Athanasios ; Piper, Andreas ; Porter, R. Jefferson ; Poskanzer, Arthur M. ; Poziombka, Stefan ; Prindle, Duncan J. ; Pühlhofer, Falk ; Rauch, Wolfgang Hans ; Reid, Jeffrey G. ; Renfordt, Rainer Arno Ernst ; Retyk, Waldemar ; Ritter, Hans Georg ; Röhrich, Dieter ; Roland, Christof ; Roland, Gunther ; Rudolph, Heinrich ; Rybicki, Andrzej ; Sakrejda, Iwona ; Sandoval, Andres ; Sann, Hans ; Semenov, Alexei Yu. ; Schäfer, Erich ; Schmischke, Dirk ; Schmitz, Norbert ; Schönfelder, Stefan ; Seyboth, Peter ; Seyerlein, Jürgen ; Siklér, Ferenc ; Skrzypczak, Ewa ; Squier, Gordon Thomas Anderson ; Stock, Reinhard ; Ströbele, Herbert ; Szentpétery, Imre ; Sziklai, János ; Toy, Milton Y. ; Trainor, Thomas A. ; Trentalange, Stephen ; Ullrich, Thomas ; Vassiliou, Maria ; Vesztergombi, György ; Vranić, Danilo ; Wang, Feipeng ; Weerasundara, Dhammika D. ; Wenig, Siegfried ; Whitten, Charles A. ; Wienold, Thomas ; Wood, Lindsay ; Yates, Tim A. ; Zimányi, József ; Zhu, Xue-Zhou ; Zybert, Ryszard
Using the NA49 main TPC, the central production of hyperons has been measured in CERN SPS Pb - Pb collisions at 158 GeV c-1. The preliminary ratio, studied at 2.0 < y < 2.6 and 1 < pT < 3 GeV c-1, equals ~ (13 ± 4)% (systematic error only). It is compatible, within errors, with the previously obtained ratios for central S + S [1], S + W [2], and S + Au [3] collisions. The fit to the transverse momentum distribution resulted in an inverse slope parameter T of 297 MeV. At this level of statistics we do not see any noticeable enhancement of hyperon production with the increased volume (and, possibly, degree of equilibration) of the system from S + S to Pb + Pb. This result is unexpected and counterintuitive, and should be further investigated. If confirmed, it will have a significant impact on our understanding of mechanisms leading to the enhanced strangeness production in heavy-ion collisions.
The thermal fit to preliminary HADES data of Au+Au collisions at sNN=2.4 GeV shows two degenerate solutions at T≈50 MeV and T≈70 MeV. The analysis of the same particle yields in a transport simulation of the UrQMD model yields the same features, i.e. two distinct temperatures for the chemical freeze-out. While both solutions yield the same number of hadrons after resonance decays, the feeddown contribution is very different for both cases. This highlights that two systems with different chemical composition can yield the same multiplicities after resonance decays. The nature of these two minima is further investigated by studying the time-dependent particle yields and extracted thermodynamic properties of the UrQMD model. It is confirmed, that the evolution of the high temperature solution resembles cooling and expansion of a hot and dense fireball. The low temperature solution displays an unphysical evolution: heating and compression of matter with a decrease of entropy. These results imply that the thermal model analysis of systems produced in low energy nuclear collisions is ambiguous but can be interpreted by taking also the time evolution and resonance contributions into account.
Mitrovski, Michael K. ; Alt, Christopher ; Antičić, Tome ; Baatar, B. ; Barna, Daniel ; Bartke, Jerzy ; Behler, Matthias ; Betev, Latchezar ; Białkowska, Helena ; Billmeier, Anja ; Blume, Christoph ; Boimska, Bożena ; Botje, Michiel ; Bracinik, Juraj ; Bramm, Roland ; Brun, René ; Bunčić, Predrag ; Cerny, Vladimír ; Christakoglou, Panagiotis ; Chvala, Ondrej ; Cramer, John G. ; Csató, Péter ; Darmenov, Nikolay ; Dimitrov, Anton ; Dinkelaker, Peter ; Eckardt, Volker ; Filip, Peter ; Fischer, Hans Gerhard ; Flierl, Dominik Bernhard ; Fodor, Zoltán ; Foka, Panagiota ; Freund, Peter ; Friese, Volker ; Gál, József ; Gaździcki, Marek ; Georgopoulos, George ; Gładysz, Ewa ; Hegyi, Sándor ; Höhne, Claudia ; Kadija, Krešo ; Karev, Alexandre ; Kliemant, Michael ; Kniege, Stefan ; Kolesnikov, Vadim I. ; Kollegger, Thorsten ; Kornaś, Ewelina ; Korus, Robert ; Kowalski, Marek ; Kraus, Ingrid ; Kreps, Michal ; Leeuwen, Marco van ; Lévai, Péter ; Litov, Leandr ; Lungwitz, Benjamin ; Makariev, Martin ; Malakhov, Aleksandr I. ; Markert, Christina ; Mateev, Matej D. ; Mayes, Bill W. ; Melkumov, Georgy L. ; Meurer, Christine ; Mischke, André ; Mitrovski, Michael Kosta ; Molnár, József ; Mrówczyński, Stanislaw ; Pálla, Gabriella ; Panagiotou, Apostolos D. ; Panayotov, Dobromir ; Perl, Katarzyna ; Petridis, Athanasios ; Pikna, Miroslav ; Pinsky, Lawrence ; Pühlhofer, Falk ; Reid, Jeffrey G. ; Renfordt, Rainer Arno Ernst ; Retyk, Waldemar ; Richard, Agnes Carol Joanna ; Roland, Christof ; Roland, Gunther ; Rybczyński, Maciej ; Rybicki, Andrzej ; Sandoval, Andres ; Sann, Hans ; Schmitz, Norbert ; Seyboth, Peter ; Siklér, Ferenc ; Sitar, Branislav ; Skrzypczak, Ewa ; Stefanek, Grzegorz ; Stock, Reinhard ; Ströbele, Herbert ; Šuša, Tatjana ; Szentpétery, Imre ; Sziklai, János ; Trainor, Thomas A. ; Varga, Dezsö ; Vassiliou, Maria ; Veres, Gábor I. ; Vesztergombi, György ; Vranić, Danilo ; Wenig, Siegfried ; Wetzler, Alexander Albert ; Włodarczyk, Zbigniew ; Yoo, In-Kwon ; Zaranek, Jacek ; Zimányi, József
A non-monotonic energy dependence of the K + / pi + ratio with a sharp maximum close to 30 A GeV is observed in central Pb+Pb collisions. Within a statistical model of the early stage, this is interpreted as a sign of the phase transition to a QGP, which causes a sharp change in the energy dependence of the strangeness to entropy ratio. This observation naturally motivates us to study the production of multistrange hyperons (Xi, Omega) as a function of the beam energy. Furthermore it was suggested that the kinematic freeze-out of Omega takes place directly at QGP hadronization. If this is indeed the case, the transverse momentum spectra of the Omega directly reflect the transverse expansion velocity of a hadronizing QGP. In this report we show preliminary NA49 results on Omega - and Omega + production in central Pb+Pb collisions at 40 and 158 A GeV and compare them to measurements of Xi - and Xi + production in central Pb+Pb collisions at 30, 40, 80 and 158 A GeV.
Mischke, André ; Afanasiev, Sergey V. ; Antičić, Tome ; Baatar, B. ; Barna, Daniel ; Bartke, Jerzy ; Barton, Robert Allan ; Betev, Latchezar ; Białkowska, Helena ; Billmeier, Anja ; Blyth, Charles O. ; Blume, Christoph ; Boimska, Bożena ; Botje, Michiel ; Bracinik, Juraj ; Bramm, Roland ; Brun, René ; Bunčić, Predrag ; Cerny, Vladimír ; Chvala, Ondrej ; Cramer, John G. ; Csató, Péter ; Dinkelaker, Peter ; Eckardt, Volker ; Filip, Peter ; Flierl, Dominik Bernhard ; Fodor, Zoltán ; Foka, Panagiota ; Freund, Peter ; Friese, Volker ; Gál, József ; Gaździcki, Marek ; Georgopoulos, George ; Gładysz-Dziaduś, Ewa ; Hegyi, Sándor ; Höhne, Claudia ; Igo, George J. ; Jones, Peter Graham ; Kadija, Krešo ; Karev, Alexandre ; Kolesnikov, Vadim I. ; Kollegger, Thorsten ; Kowalski, Marek ; Kraus, Ingrid ; Kreps, Michal ; Leeuwen, Marco van ; Lévai, Péter ; Malakhov, Aleksandr I. ; Margetis, Spyridon ; Markert, Christina ; Mayes, Bill W. ; Melkumov, Georgy L. ; Meurer, Christine ; Mitrovski, Michael Kosta ; Molnár, József ; Nelson, John M. ; Pálla, Gabriella ; Panagiotou, Apostolos D. ; Perl, Katarzyna ; Petridis, Athanasios ; Pikna, Miroslav ; Pinsky, Lawrence ; Pühlhofer, Falk ; Reid, Jeffrey G. ; Renfordt, Rainer Arno Ernst ; Retyk, Waldemar ; Roland, Christof ; Roland, Gunther ; Rybicki, Andrzej ; Sammer, Thomas ; Sandoval, Andres ; Sann, Hans ; Schmitz, Norbert ; Seyboth, Peter ; Siklér, Ferenc ; Sitar, Branislav ; Skrzypczak, Ewa ; Squier, Gordon Thomas Anderson ; Stock, Reinhard ; Ströbele, Herbert ; Šuša, Tatjana ; Szentpétery, Imre ; Sziklai, János ; Trainor, Thomas A. ; Varga, Dezsö ; Vassiliou, Maria ; Veres, Gábor I. ; Vesztergombi, György ; Vranić, Danilo ; Wenig, Siegfried ; Wetzler, Alexander Albert ; Whitten, Charles A. ; Yoo, In-Kwon ; Zaranek, Jacek ; Zimányi, József
Rapidity distributions for $\Lambda$ and $\bar{\Lambda}$ hyperons in central Pb-Pb collisions at 40, 80 and 158 A$\cdot$GeV and for ${\rm K}_{s}^{0}$ mesons at 158 A$\cdot$GeV are presented. The lambda multiplicities are studied as a function of collision energy together with AGS and RHIC measurements and compared to model predictions. A different energy dependence of the $\Lambda/\pi$ and $\bar{\Lambda}/\pi$ is observed. The $\bar{\Lambda}/\Lambda$ ratio shows a steep increase with collision energy. Evidence for a $\bar{\Lambda}/\bar{\rm p}$ ratio greater than 1 is found at 40 A$\cdot$GeV.