Transcript for the ... Particle Production at Very Low and Intermediate Adam Trzupek

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
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
INSTITUTE OF NUCLEAR PHYSICS PAN, KRAKOW
NATIONAL CENTRAL UNIVERSITY, TAIWAN
UNIVERSITY OF MARYLAND
BROOKHAVEN NATIONAL LABORATORY
MASSACHUSETTS INSTITUTE OF TECHNOLOGY
UNIVERSITY OF ILLINOIS AT CHICAGO
UNIVERSITY OF ROCHESTER
Particle Production at Very Low pT
PHOBOS experiment has a
unique capability to measure
particles down to very small
transverse momenta:
0.03 - 0.2 GeV/c
Enhanced production of low-pT
particles was predicted as
a consequence of NEW long
wave-length phenomena
BULK
Au+Au, 200 GeV
centrality: 0-15%
mid-rapidity
PHOBOS:
 PRC 70 (2004) 051901(R)
 PLB 578 (2004) 297
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
pT and PID Measurement in PHOBOS Spectrometer
10 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
z
-x
E
F
X[cm]
D
C
B
• pT > 0.2 GeV/c
track curvature in B field
dE/dx in Si, ToF
p,charge
mass
• pT = 0.03 - 0.2 GeV/c
low-p particles stop
in silicon wafers
p, mass
A
B field negligible
.
.
Be pipe
0
10
20 Z [cm]
no charge
identification
PHOBOS PID Capabilities
1/v (ps/cm)
PRC 70 (2004) 051901(R)
p+p
K++K -
70
60
50
40
++-
30
p (GeV/c)
Eloss (MeV)
Stopping
particles
0.03
0
dE/dx
0.5
1
2
4
3
p (GeV/c)
TOF
5.0
pT (GeV/c)
Particle ID from low to high pT
5
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
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]
(2pT)1d2N/dydpT[c2/GeV2]
Low-pT Spectra of Identified
Particles in Au+Au Collisions
at sNN =62.4 GeV
(2pT)1d2N/dydpT[c2/GeV2]
Low-pT Spectra of Identified Particles
Au+Au at sNN = 200 GeV
B-E fit
BWF fit
PHOBOS, PR C70, 051901 (R) (2004)
PHENIX, PR C69, 034909 (2004)
1 1 d 2N
1
 A exp(mT /TBE ) 
 1
2 mT dydmT
mT = pT2+mh2
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
(2pT)1d2N/dydpT[c2/GeV2]
(2pT)1d2N/dydpT[c2/GeV2]
Invariant Yields of Very Low pT Particles
in Central Au+Au Collisions at sNN=200 GeV
(2pT)1d2N/dydpT[c2/GeV2]
Low-pT Spectra as Model Constraints
J. Cramer (private comm.,
erratum to be published)
J.Cramer, et al.,
PRL 94 (2005) 102302
(2pT)1d2N/dydpT[c2/GeV2]
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
Tfo = 152 GeV, <T>=0.37 c
mT -Scaling in d+Au at sNN= 200 GeV
-
Tloc[GeV/c2]
(++-), (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
mT -Scaling in d+Au vs. Au+Au at sNN = 200 GeV
(2pT)1d2N/dydpT[c2/GeV2]
(2pT)1d2N/dydpT[c2/GeV2]
Tloc[GeV/c2]
Tloc[GeV/c2]
PRC 70 (2004) 051901(R)
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
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