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Particle Production at Very Low and Intermediate Transverse Momenta in d+Au and Au+Au Collisions

Particle Production at Very Low and Intermediate Transverse Momenta in d+Au and Au+Au Collisions. Adam Trzupek The Henryk Niewodniczański Institute of Nuclear Physics Polish Academy of Sciences Kraków, Poland. for the Collaboration. Quark Matter 2005

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Particle Production at Very Low and Intermediate Transverse Momenta in d+Au and Au+Au Collisions

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  1. Particle Production at Very Low and Intermediate Transverse Momenta in d+Au and Au+Au Collisions Adam Trzupek The Henryk Niewodniczański Institute of Nuclear Physics Polish Academy of Sciences Kraków, Poland for the Collaboration Quark Matter 2005 18th International Conference on Ultra-Relativistic Nucleus-Nucleus Collisions, Budapest, Hungary

  2. Collaboration (August 2005) Burak Alver, Birger Back,Mark Baker, Maarten Ballintijn, Donald Barton, Russell Betts, Richard Bindel, Wit Busza (Spokesperson), Zhengwei Chai, Vasundhara Chetluru, Edmundo García, Tomasz Gburek, Kristjan Gulbrandsen, Clive Halliwell, Joshua Hamblen, Ian Harnarine, Conor Henderson, David Hofman, Richard Hollis, Roman Hołyński, Burt Holzman, Aneta Iordanova, Jay Kane,Piotr Kulinich, Chia Ming Kuo, Wei Li, Willis Lin, Constantin Loizides, Steven Manly, Alice Mignerey, Gerrit van Nieuwenhuizen, Rachid Nouicer, Andrzej Olszewski, Robert Pak, Corey Reed, Eric Richardson, Christof Roland, Gunther Roland, Joe Sagerer, Iouri Sedykh, Chadd Smith, Maciej Stankiewicz, Peter Steinberg, George Stephans, Andrei Sukhanov, Artur Szostak, Marguerite Belt Tonjes, Adam Trzupek, Sergei Vaurynovich, Robin Verdier, Gábor Veres, Peter Walters, Edward Wenger, Donald Willhelm, Frank Wolfs, Barbara Wosiek, Krzysztof Woźniak, Shaun Wyngaardt, Bolek Wysłouch ARGONNE NATIONAL LABORATORY BROOKHAVEN NATIONAL LABORATORY INSTITUTE OF NUCLEAR PHYSICS PAN, KRAKOW MASSACHUSETTS INSTITUTE OF TECHNOLOGY NATIONAL CENTRAL UNIVERSITY, TAIWAN UNIVERSITY OF ILLINOIS AT CHICAGO UNIVERSITY OF MARYLAND UNIVERSITY OF ROCHESTER

  3. Particle Production at Very Low pT Au+Au, 200 GeV centrality: 0-15% mid-rapidity PHOBOS:  PRC 70 (2004) 051901(R) PLB 578 (2004) 297 PHOBOS experiment has a unique capability to measure particles down to very small transverse momenta: 0.03 - 0.2 GeV/c BULK Enhanced production of low-pT particles was predicted as a consequence of NEW long wave-length phenomena TAIL Particle spectra at low pT can be modified due to collective transverse expansion A recent optical model implies that chiral symmetry restoration can have significant impact on shapes of pion spectra at very low pT J.Cramer, et al., Phys. Rev. Lett. 94 (2005) 102302

  4. pT > 0.2 GeV/c • track curvature in B field p,charge • dE/dx in Si, ToF mass • pT = 0.03 - 0.2 GeV/c • low-pparticles stop • in silicon wafers p, mass • B field negligible no charge identification z -x F E D C X[cm] B A . . Be pipe 01020Z [cm] . pT and PID Measurement in PHOBOS Spectrometer 70 cm • PHOBOS Spectrometer • 16 layers of silicon wafers • fine pixelization, precise dE measurement • collision vertex close to spectrometer • near mid-rapidity coverage • dipole magnetic field of 2T at maximum 10 cm

  5. 70 60 50 + - K+K 40 30 0 5 4 2 3 1 p (GeV/c) Particle ID from low to high pT PHOBOS PID Capabilities PRC 70 (2004) 051901(R) p+p 1/v (ps/cm) ++- Eloss(MeV) p (GeV/c) Stopping particles dE/dx TOF 5.0 0.5 0.03 pT (GeV/c)

  6. Identified Particle pT -Spectra, Au+Au at 62.4 GeV These results at 62.4 GeV fit smoothly into the energy evolution of antiparticle/particle ratios

  7. Low-pT Spectra of Identified Particles in Au+Au Collisions at sNN =62.4 GeV (2pT)1d2N/dydpT[c2/GeV2] Blast wave fit parameters: 0-15%: Tfo = 99 MeV, <T>=0.51 c 15-30%: Tfo = 98 MeV, <T>=0.51 c 30-50%: Tfo = 97 MeV, <T>=0.49 c (2pT)1d2N/dydpT[c2/GeV2] (2pT)1d2N/dydpT[c2/GeV2]

  8. mT = pT2+mh2  Low-pT Spectra of Identified Particles Au+Au at sNN = 200 GeV B-E fit PHOBOS, PR C70, 051901 (R) (2004) PHENIX, PR C69, 034909 (2004) BWF fit (2pT)1d2N/dydpT[c2/GeV2] T= 229 MeV for (++-) 293 MeV for (K++ K-) 392 MeV for (p + p) Blast Wave Fit: Tfo= 99 MeV <T> = 0.54 c No enhancement in low-pT yields for pions is observed Flattening of (p+p) spectra down to very low pT, consistent with transverse expansion of the system

  9. Invariant Yields of Very Low pT Particlesin Central Au+Au Collisions at sNN=200 GeV (2pT)1d2N/dydpT[c2/GeV2] (2pT)1d2N/dydpT[c2/GeV2]

  10. Low-pT Spectra as Model Constraints (2pT)1d2N/dydpT[c2/GeV2] J. Cramer (private comm., erratum to be published) J.Cramer, et al., PRL 94 (2005) 102302

  11. Identified Particle pT -Spectra, d+Au at sNN= 200 GeV • pT range: • (++-) : > 0.03 GeV/c • (K++ K-): > 0.09 GeV/c • (p + p) : > 0.14 GeV/c • Background corrections: • very low-pT: • (++-) : 20% • (K++ K-): 10% • (p + p) : 20% • intermediate pT • (p + p) : ~20% • Systematic uncertainties: • very low pT: ~30% • intermediate pT : ~15% • Event selection: • described in PRL 93, 082301 (2pT)1d2N/dydpT[c2/GeV2] Tfo = 152 GeV, <T>=0.37 c

  12. mT -Scaling in d+Au at sNN= 200 GeV (++-), (K++ K-), (p + p) mT-yields are similar after scaling (K++ K-) yield by a factor 2 (strangeness suppression) Local slopes of mT -spectra similar Tloc[GeV/c2]

  13. mT -Scaling in d+Au vs. Au+Au at sNN = 200 GeV PRC 70 (2004) 051901(R) (2pT)1d2N/dydpT[c2/GeV2] (2pT)1d2N/dydpT[c2/GeV2] Tloc[GeV/c2] Tloc[GeV/c2] In central Au+Au, larger flattening for of p+p mT spectra at small pT Low-pT spectra of p+p can constrain models describing collective transverse expansion of the system

  14. Summary • No evidence for enhanced production of very low-pT pions iaiiin the mosticentral Au+Au collisions at energy 62.4 and iaii200 GeV • Flattening of p+p mT spectra at low-pT in 15% most central iaiiAu+Au collisions at energy 62.4 and 200 GeV • Approximate mT scaling of particle spectra for d+Au iaiicollisions at low and intermediate transverse momentum • New constraints on models and fits

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