Results and Perspectives

AGS & RHIC Users Meeting, June 23, 2005AGS & RHIC Users Meeting, June 23, 2005

Results and Perspectives

Gábor I. VeresEötvös Loránd University, Budapest and

Massachusetts Institute of Technology, Cambridge

for the collaboration

RHIC & AGS Annual Users’ Meeting

June 23, 2005

PHOBOS Workshop talks:George Stephans - Femtoscopy (Tue 6/21)Zhengwei Chai - Multiplicity Fluctuations (Tue 6/21)

PHOBOS Posters by: Abigail Bickley, Richard Hollis, Carla Vale

Gábor I. Veres AGS & RHIC Users Meeting, June 23, 2005AGS & RHIC Users Meeting, June 23, 2005

Another year of spectacular achievement for RHIC & C-AD THANKS!!!

Run 5 is the most diverse run so far:

• 9 weeks of Cu+Cu at 200 GeV (6 nb-1)

• 2 weeks of Cu+Cu 62.4 GeV (0.25 nb-1)

• 2 days of Cu+Cu 22.5 GeV

• few hours of p+p at 410 and 200 GeV

CuCu@200 [email protected]


The Collaboration (June 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, 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 LABORATORYINSTITUTE OF NUCLEAR PHYSICS PAN, KRAKOW MASSACHUSETTS INSTITUTE OF TECHNOLOGY

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


Outline

• What did we learn in the five years of PHOBOS history?

• Results since the last Users’ Meeting

• Plans and perspectives of PHOBOS


5 years of PHOBOS…

Data we took in various runs:

p+p d+Au Cu+Cu Au+Au410 5200 2,3,4,5 3 5 2,4130 162.4 5 455.9 122.5 519.6 2

GeVsystem


PHOBOS: number of events on tape…

p+p d+Au Cu+Cu Au+Au410 20200 100 150 400 250130 4.362.4 110 2255.9 1.822.5 2019.6 ~1

GeVsystem

[in millions]


Evolution of the detector – Pre-run 1: AuAu


Run 1: Au+Au

AGS & RHIC Users Meeting, June 23, 2005AGS & RHIC Users Meeting, June 23, 2005

Run 2: Au+Au and p+p


Run 3: d+Au and p+p


Run 4 and 5: Au+Au, Cu+Cu


Run 4 and 5: p+p


Run 6…


Data rate and number of events taken

Run 2

Run 3

Run 4

Run 5All-inclusive count,

Including tests

Continuous DAQ upgrades!

Over a billion events taken


The PHOBOS computing architecture… to cope with hundreds of millions of events

Internet

Master

Slave

Slave

Slave

Slave

User

PROOF

CatWeb – data management (650k files, 400 TByte)• Easy www interface to stage HPSSRCF•API for access to functionality from ROOT/PhAT

AnT – Analysis Tree DST format• ROOT Tree based, fast access to subsets of data• Well structured, links hits to tracks etc.

PROOF – Parallel ROOT Facility• Parallel interactive analysis, over x100 speed-up!• Co-exist with regular batch usage

Distributed disks• 100 TByte, fast access • ALL physics data is stored on disks!


PHOBOS physics publications

The PHOBOS Perspective on Discoveries at RHICScaling of Charged Particle Production in d+Au Collisions at sqrt(s_NN)=200 GeVCharged antiparticle to particle ratios near midrapidity in p+p collisions at sqrt(s_NN) = 200 GeVTransverse momentum and rapidity dependence of HBT correlations in Au+Au collisions at sqrt(s_NN) = 62.4 and 200 GeVCentrality and pseudorapidity dependence of elliptic flow for charged hadrons in Au+Au collisions at sqrt(s_NN)= 200 GeVEnergy dependence of elliptic flow over a large pseudorapidity range in Au+Au collisions at RHICPseudorapidity dependence of charged hadron transverse momentum spectra in d+Au collisions at sqrt(s_NN)=200 GeVCollision Geometry Scaling of Au+Au pseudorapidity density from sqrt(s_NN) = 19.6 to 200 GeVCentrality dependence of charged hadron transverse momentum spectra in Au+Au collisions from sqrt(s_NN) = 62.4 to 200 GeVParticle production at very low transverse momenta in Au+Au collisions at sqrt(s_NN)=200 GeVPseudorapidity Distribution of Charged Particles in d+Au collisions at sqrt(s_NN)=200 GeVCentrality dependence of charged antiparticle to particle ratios near mid-rapidity in d+Au collisions at sqrt(s_NN)=200 GeVCentrality Dependence of the Charged Hadron Transverse Momentum Spectra in d+Au Collisions at sqrt(sNN)=200 GeV

Charged hadron transverse momentum distributions in Au+Au collisions at sqrt(s_NN) = 200 GeVComparison of the Total Charged-Particle Multiplicity in High-Energy Heavy Ion Collisions with e+e- and pp/pbar-p DataSignificance of the fragmentation region in ultrarelativistic heavy ion collisionsRatios of charged antiparticles to particles near mid-rapidity in Au+Au collisions at sqrt(sNN)=200 GeV

Pseudorapidity and centrality dependence of the collective flow of charged particles in Au+Au collisions at sqrt(sNN)=130 GeV

Centrality Dependence of the Charged Particle Multiplicity near Mid-Rapidity in Au+Au Collisions at sqrt(sNN)=130 and 200 GeV

Energy dependence of particle multiplicities near mid-rapidity in central Au+Au collisions Centrality Dependence of Charged Particle Multiplicity at Midrapidity in Au+Au Collisions at sqrt(sNN)=130 GeV

Charged-particle pseudorapidity density distributions from Au+Au collisions at sqrt(sNN)=130 GeV

Ratios of charged particles to antiparticles near mid-rapidity in Au+Au collisions at sqrt(sNN)=130 GeV

Charged particle multiplicity near mid-rapidity in central Au+Au collisions at sqrt(s) = 56 and 130 AGeV

24 papers, including 12 in Phys. Rev. Letters


“White Paper”: summary of PHOBOS results

• We have created a state of matter at RHIC with high energy-density, that is nearly net-baryon free and interacting very strongly.

• Transition to this high-energy state of matter does not create abrupt changes in observables at RHIC energies.

• The data exhibit “simple” scaling behavior and factorization. → suggests strong global constraints and illustrates the importance of the collision geometry in the initial state and the early evolution of the colliding system.

nucl-ex/0410022, Nucl. Phys. A 757, 28


High energy density & nearly baryon-free matter

Energy Density Estimate: RHIC > 3 GeV/fm3

Energy density ~6x that of nucleons (20x that of nuclei)

Particle Ratios:Approaching Unity

B at full RHIC energy is a factor ~10 smaller than at SPS.

(Our new result is p+p@200GeV)

A+A

p+p


Strongly interacting matter…

• Elliptic flow reaches hydro limit• Suppressed high-pT production• No enhanced low-pT production

PHOBOS nucl-ex/0407012…flow

PHOBOS PRC 70, 051901(R)…low-pT

00

0.5

1.0

1.5

RA

A, R

dA

u

Au+Au 0-6%

d+Au 0-20%

…high-pT PHOBOS PRL 91, 072302PHOBOS PRC 70, 061901

d+Au

200 GeV Au+Au, 0-50%

hydro

200 GeV Au+Au


200 GeV Au+Au


Recent theoretical interest at low pT

Phobos 15% data Estimated extrapolation to 5%

data: (Au+Au 15% central

(George Stephans’ talk)J. G. Cramer et al., Phys. Rev. Lett. 94, 102302 (2005)

and PHOBOS comment: nucl-ex/0506008


PHOBOS nucl-ex/0407012

v2

Npart

Transition is gradual, not abrupt…

62.4 GeV200 GeV

PHOBOS PRL 94, 082304

…vs. energy

Au+Au

Track-based 200 GeVHit-based 200 GeVHit-based 130 GeV

PHOBOS Nucl.Phys.A 757,28

AG

SSP

S

PHO

BO

S

…vs. centrality


Extended longitudinal scaling…

PHOBOS PRL 94, 122303

PHOBOS nucl-ex/0409021

…in dN/dp+p, d+Au, Au+Au):

…in v2 (elliptic flow):

d+Au


Universality of Nch

PHOBOS nucl-ex/0301017 & Nucl. Phys. A 757, 28

Npart scaling: Au+Au, d+Au

e+e-, p+p, A+A data

produces the same Nch

d+Aup+p

Au+Au


Factorization of geometry and energy

Ratio of dN/d=0 at different energies:

Also differentially, at various pT values:

200/19.6 GeV

200/130 GeV

R(2

00/X

)

200/62.4 GeV

0.25<pT>= 1.25 2.50 3.38 3.88 GeV/c

<Npart>


Our most recent results: dN/d in Au+Au at 62.4 GeV

PHOBOS

preliminary• most recent Au+Au run

• B field off

• 2 centrality methods:

scint. paddles at 3.2<<4.5

octagon ||<3

• 3 different dN/d methods:

analog, digital, ‘tracklets’


The most central data compared to other energies

PHOBOS

preliminary


Our new 64.2 GeV point fits into the trend

• Mid-rapidity yields in

~6% most central events

• Logarithmic rise

A+Ap+p(p)

PHOBOSpreliminary


Factorization of beam energy and collision geometry is also valid at 62.4 GeV

• at higher energies, hard collisions

should be more dominant

• Ncoll/Npart increases with centrality

• still, energy-independent

centrality evolution

Factorization of energy

and collision geometry

PHOBOS

preliminary


Extended longitudinal scaling of charged hadrons(Also in d+Au and in v2)

PHOBOS

preliminary


RPC is precisely energy independentNpart

Ratio of 0-6% and 35-40% centrality bins, each normalized by Npart

90% C.L. syst. errors

PHOBOS

preliminary


Total charged particle yields: Npart scaling

Error bands from the

extrapolation to high

PHOBOS

preliminary

• Integrated over the full range

• Nch is linearly increasing with Npart

• “wounded nucleon scaling”

• Scaled multiplicity is higher than in p+p


Plans, PerspectivesData taking for PHOBOS has ended, but…

…lots of data on tape, still to be analyzed in the next years:

• Charged hadron spectra in Cu+Cu, p+Au, n+Au collisions

• Identified spectra and particle/antiparticle ratios (Cu+Cu, Au+Au)

• Particle production at very low pT (G. Stephans’ talk)

• Measurement of the Φ meson

• Multiplicity analysis using ‘tracklets’ and digital/analog method

• Event-by-event multiplicity fluctuations (Z. Chai’s talk)

• Two-particle correlations in d+Au collisions

• Elliptic and directed flow measurements

• Rare event searches

• etc… More news to come!


Summary• Another great year for RHIC (& PHOBOS)

– “White Paper” reviews from the four experiments– Spectacular and diverse run with many different

collisions, and upgraded DAQ and computing• Luminosities even exceeding the goals

• Multiplicity measurement at 62.4 GeV– Fits into the known evolution with energy– Various scaling features observed/confirmed– Data are simpler than the models!

• Lot of data is still preliminary/in the works: – Much more results to come in the (near) future!

…see you in Budapest!



Results and Perspectives

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