charged hadron p t spectra from au+au at s nn = 62.4 gev

Conor Henderson, MITDivision of Nuclear Physics, Chicago, 2004

Charged Hadron pT Spectra from Au+Au at sNN = 62.4 GeV

Conor Henderson, MIT

For the collaboration

Division of Nuclear Physics, Chicago

29 October 2004


Collaboration (October 2004)

Burak Alver, Birger Back, Mark Baker, Maarten Ballintijn, Donald Barton, Russell Betts, Abigail

Bickley,

Richard Bindel, Wit Busza (Spokesperson), Alan Carroll, Zhengwei Chai, Vasundhara Chetluru,

Patrick Decowski, Edmundo García, Tomasz Gburek, Nigel George, Kristjan Gulbrandsen,

Clive Halliwell, Joshua Hamblen, Ian Harnarine, Conor Henderson, David Hofman, Richard Hollis,

Roman Hołyński, Burt Holzman, Aneta Iordanova, Jay Kane, Nazim Khan, Piotr Kulinich,

Chia Ming Kuo, Wei Li, Willis Lin, Steven Manly, Alice Mignerey, Gerrit van Nieuwenhuizen,

Rachid Nouicer, Andrzej Olszewski, Robert Pak, Heinz Pernegger, Corey Reed, Christof Roland,

Gunther Roland, Joe Sagerer, Iouri Sedykh, Wojtek Skulski, Chadd Smith, Maciej Stankiewicz,

Peter Steinberg, George Stephans, Andrei Sukhanov, Marguerite Belt Tonjes, Adam Trzupek,

Carla Vale, Sergei Vaurynovich, Robin Verdier, Gábor Veres, Peter Walters, Edward Wenger,

Frank Wolfs, Barbara Wosiek, Krzysztof Woźniak, Alan Wuosmaa, Bolek Wysłouch

ARGONNE NATIONAL LABORATORY BROOKHAVEN NATIONAL LABORATORYINSTITUTE OF NUCLEAR PHYSICS PAN, KRAKOW MASSACHUSETTS INSTITUTE OF TECHNOLOGY

NATIONAL CENTRAL UNIVERSITY, TAIWAN UNIVERSITY OF ILLINOIS AT CHICAGOUNIVERSITY OF MARYLAND UNIVERSITY OF ROCHESTER

Conor Henderson, MITDivision of Nuclear Physics, Chicago, 2004Spectrometer

Paddle Trigger Counter

137000 Silicon Pad ChannelsT0 counter

PHOBOS Detector 2004

NIM A 499, 603-623 (2003)


Centrality Range Studied at 62.4 GeV

Centrality <Npart> <Ncoll>

45-50% 61 7 85 14

35-45% 86 9 136 22

25-35% 130 10 240 30

15-25% 189 9 402 36

6-15% 266 9 643 48

0-6% 335 11 883 65


Charged Hadron pT SpectraCorrected for:

• Acceptance

• Efficiency

• Feed-down

• Secondaries

• Momentum resolution

• Ghosts

• Bin width

• Dead channelsnucl-ex/0405003


RAA for Au+Au at sNN = 62.4 GeV

• RAA significantly higher at 62.4 GeV than at 200 GeV


RAA at 62.4 GeV from Theory (I)

Vitev:

nucl-th/0404052

XN Wang:

nucl-th/0405029

Adil, Gyulassy:

nucl-th/0405036

• From parton energy loss calculations:


RAA at 62.4 GeV from Theory (II)

Eskola, Honkanen, Salgado,

Wiedemann: hep-ph/0406319

Gallmeister, Cassing: hep-ph/0408223


Factorization of Energy and Centrality Dependence

• Centrality dependence of

vs. pT is the same at both energies

• Challenge to collision models to reproduce this


Factorization for Particle MultiplicityPHOBOS, Phys. Rev. C70, 021902(R) (2004)

• Factorization also seen for mid-rapidity multiplicity, from 19.6 to 200 GeV


PHOBOS PID Capabilities at 62.4 GeV

dE/dx in Silicon Time-of-flight


Conclusions

• PHOBOS has measured h pT spectra up to 4 GeV in Au+Au collisions at sNN = 62.4 GeV

• RAA significantly higher at 62.4 GeV than at 200 GeV

• But the centrality dependence of the pT yields found to be remarkably similar at the two energies - this factorization also seen in mid-rapidity particle yields from 19.6 to 200 GeV

• Appears to be a key feature of heavy-ion collisions which remains to be understood


Back-up Slides


The PHOBOS Spectrometer

z

y

70 cm 10cm

x

• Silicon sensors• Outer layers in 2T

magnetic field• High segmentation in

bending direction • Tracking within 10 cm

of interaction point

• Coverage near mid-rapidity


Definitions


Centrality Range at 200 GeV

Centrality <Npart> <Ncoll>

45-50% 65 4 99 11

35-45% 93 5 164 15

25-35% 138 6 286 25

15-25% 200 8 483 40

6-15% 276 9 762 57

0-6% 344 11 1040 77


Centrality Range at 62.4 & 200 GeV


Npart and Ncoll vs. sNN

• Nucleon-nucleon inelastic cross-section grows with collision energy

• So Ncoll/Npart increases with sNN


RAANpart and RPC

Npart


RPCNpart vs. Npart in pT bins for 200GeV


Z Phys. C 69, 55 (1995)

Nucl. Phys. B 207, 1 (1982)

Phys. Lett. B 83, 257 (1979)

Nucl. Phys. B 335, 261 (1990)

p+p Reference Spectrum at 62.4 & 200 GeV

SFM @ISR


PHOBOS and STAR at 200 GeV

PLB 578297, 2004

PRL 91, 172302, 2003


PHENIX pT Spectra at sNN = 200 GeV

Insert PHENIX reference


RAA at 62.4 GeV from Theory (IV)

Adil, Gyulassy: nucl-th/0405036


RAA at 62.4 GeV from Theory (II)

Eskola, Honkanen, Salgado, Wiedemann: hep-ph/0406319

• pQCD collinearly factorized formalism with radiative parton energy loss


RAA at 62.4 GeV from Theory (III)Gallmeister, Cassing: hep-ph/0408223

• Hadron string dynamical transport model

• Hadron attenuation attributed to inelastic collisions of leading pre-hadron with dense hadronic medium

charged hadron p t spectra from au+au at s nn = 62.4 gev

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