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

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Particle Production at Very Low and Intermediate
Transverse Momenta in dAu and AuAu Collisions
Adam Trzupek The Henryk Niewodniczanski 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
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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 Holynski,
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 Wozniak, Shaun
Wyngaardt, Bolek Wyslouch ARGONNE NATIONAL
LABORATORY BROOKHAVEN NATIONAL LABORATORY INSTITU
TE OF NUCLEAR PHYSICS PAN, KRAKOW MASSACHUSETTS
INSTITUTE OF TECHNOLOGY NATIONAL CENTRAL
UNIVERSITY, TAIWAN UNIVERSITY OF ILLINOIS AT
CHICAGO UNIVERSITY OF MARYLAND UNIVERSITY OF
ROCHESTER
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Particle Production at Very Low pT
AuAu, 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
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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
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PHOBOS PID Capabilities
PRC 70 (2004) 051901(R)
pp
1/v (ps/cm)
??-
Eloss (MeV)
p (GeV/c)
Stopping particles
dE/dx
TOF
5.0
0.5
0.03
pT (GeV/c)
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Identified Particle pT -Spectra, AuAu at 62.4
GeV
These results at 62.4 GeV fit smoothly into the
energy evolution of antiparticle/particle ratios
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Low-pT Spectra of Identified Particles in AuAu
Collisions at ?sNN 62.4 GeV
(2?pT)?1d2N/dydpTc2/GeV2
Blast wave fit parameters 0-15 Tfo 99 MeV,
lt?Tgt0.51 c 15-30 Tfo 98 MeV, lt?Tgt0.51
c 30-50 Tfo 97 MeV, lt?Tgt0.49 c
(2?pT)?1d2N/dydpTc2/GeV2
(2?pT)?1d2N/dydpTc2/GeV2
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Low-pT Spectra of Identified Particles AuAu at
?sNN 200 GeV
B-E fit
PHOBOS, PR C70, 051901 (R) (2004) PHENIX, PR C69,
034909 (2004)
BWF fit
(2?pT)?1d2N/dydpTc2/GeV2
T 229 MeV for (??-) 293 MeV for (K
K-) 392 MeV for (p p)
Blast Wave Fit Tfo 99 MeV
lt?Tgt 0.54 c
No enhancement in low-pT yields for pions is
observed Flattening of (pp) spectra down to
very low pT, consistent with transverse
expansion of the system
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Invariant Yields of Very Low pT Particlesin
Central AuAu Collisions at ?sNN200 GeV
(2?pT)?1d2N/dydpTc2/GeV2
(2?pT)?1d2N/dydpTc2/GeV2
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Low-pT Spectra as Model Constraints
(2?pT)?1d2N/dydpTc2/GeV2
J. Cramer (private comm., erratum to be published)
J.Cramer, et al., PRL 94 (2005) 102302
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Identified Particle pT -Spectra, dAu at ?sNN
200 GeV
pT range (??-) gt 0.03 GeV/c (K K-) gt
0.09 GeV/c (p p) gt 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/dydpTc2/GeV2
Tfo 152 GeV, lt?Tgt0.37 c
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mT -Scaling in dAu 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
TlocGeV/c2
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mT -Scaling in dAu vs. AuAu at ?sNN 200 GeV
PRC 70 (2004) 051901(R)
(2?pT)?1d2N/dydpTc2/GeV2
(2?pT)?1d2N/dydpTc2/GeV2
TlocGeV/c2
TlocGeV/c2
In central AuAu, larger flattening for of pp mT
spectra at small pT Low-pT spectra of pp can
constrain models describing collective transverse
expansion of the system
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Summary

• No evidence for enhanced production of very
  low-pT pions iaiiin the mosticentral AuAu
  collisions at energy 62.4 and iaii200 GeV
• Flattening of pp mT spectra at low-pT in 15
  most central iaiiAuAu collisions at energy 62.4
  and 200 GeV
• Approximate mT scaling of particle spectra for
  dAu iaiicollisions at low and intermediate
  transverse momentum
• New constraints on models and fits