brahms 22. oktober 2004 forward physics workshop, ku i.g.bearden, niels bohr institute 1 brahms...

22. Oktober 2004 Forward Physics Workshop, KUI.G.Bearden, Niels Bohr Institute

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BRAHMS

Particle Production Studied with

BRAHMSBRAHMSI.G. Bearden,

Niels Bohr Institute For

The BRAHMS collaboration


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BRAHMS

The BRAHMS Collaboration

I.Arsene10,I.G. Bearden7, D. Beavis1, C. Besliu10, Y. Blyakhman6, J.Brzychczyk4, B. Budick6,H. Bøggild7 ,C. Chasman1, C. H. Christensen7, P. Christiansen7,

J.Cibor4,R.Debbe1,J. J. Gaardhøje7,M. Germinario7, K. Hagel8, O. Hansen7, H. Ito11, E. Jacobsen7, A. Jipa10, J. I. Jordre10, F. Jundt2,

C.E.Jørgensen7, E. J. Kim5, T. Kozik3, T.M.Larsen12, J. H. Lee1, Y. K.Lee5, G. Løvhøjden2, Z. Majka3, A. Makeev8, B. McBreen1, M. Murray8, J. Natowitz8, B. Neuman11,B.S.Nielsen7, K. Olchanski1, D. Ouerdane7, R.Planeta4, F. Rami2,

D. Roehrich9, B. H. Samset12, S. J. Sanders11, I. S. Sgura10, R.A.Sheetz1, Z.Sosin3, P. Staszel7, T.S. Tveter12, F.Videbæk1, R. Wada8 ,A.Wieloch3,Z. Yin9

1Brookhaven National Laboratory, USA, 2IReS and Université Louis Pasteur, Strasbourg, France3Jagiellonian University, Cracow, Poland, 4Institute of Nuclear Physics, Cracow, Poland

5Johns Hopkins University, Baltimore, USA, 6New York University, USA7Niels Bohr Institute, Blegdamsvej 17, University of Copenhagen, Denmark

8Texas A&M University, College Station. USA, 9University of Bergen, Norway 10University of Bucharest, Romania, 11University of Kansas, Lawrence,USA

12 University of Oslo Norway

- 12 institutions-


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BRAHMS

Two small solid anglespectrometers (FS and MRS)

2.3°30°

that can rotate from 2.3° to 30°

90°

30°

and 30° to 90° (MRS)

provide excellent PID over broad range in y-pT

The BRAHMS ExperimentIt’s Broad RAnge Hadron Magnetic Spectrometers!


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BRAHMS

K

p

BRAHMS Acceptance:


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BRAHMS

A BRAHMS Event

TPM2

TPM1D5

D1T1

D2T2

beam

beamcollision point(vertex)

MRS at 90 degrees

FFS at 6 degrees

Reconstructed tracks


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BRAHMS

Event CountingWe want to make spectra,

we need to count the numberof collisions (events) Nevents and the number of tracks Ntracks

…still we need the centrality from the multiplicity (MA)…

multiplicity [a.u.]

T

tracks

Tevents dpd

dN

pN η211

…and the collision point (vertex) from the BB, ZDC and INEL counters.

MA

INEL

ZDC ZDCBB BB

We measure (almost) all the collisions and counting is easy!


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BRAHMSCharged Particle Multiplicity

dN/dη According to Bjorken,

>5GeV/fm3

170MeV

T

B


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BRAHMS

After appropriate corrections, we combine all data sets to obtainfinal invariant yields over a broad range of rapidity and pT

Particle Spectra

K

p


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BRAHMS

n

T

p

pA

−

⎟⎟⎠

⎞⎜⎜⎝

⎛+

0

1

Pions: power law Kaons:exponential

⎟⎠

⎞⎜⎝

⎛ −−

T

mmA Texp

Protons: Gaussian

⎥⎦

⎤⎢⎣

⎡−

2

2

2exp

σTpA

Top 5% central collisions Spectra:


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BRAHMS

Integrated multiplicities (Gaussian fit)

N() ~ 1780 N(+) ~1760N(K+) ~ 290 N(K) ~ 240N(pbar) ~ 85

Rapidity DensitiesAt y ~ 0, dN/dy is ~ 300 (300) for + (-) ~ 47 (44) for K+ (K) ~ 27 (20) for p (pbar) N() >> N(K) > N(p)N(+) = N()N(K+) > N(K) and N(p) > N(pbar) systematically


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BRAHMS

BRAHMS, submittedto PRL, 31/12/03nucl-ex/0312023P. Christiansen Ph.D. Thesis, København’s Universitet

protons

antiprotons

Proton & antiproton dN/dy (5% central)


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BRAHMS

BRAHMS, submittedto PRL, 31/12/03nucl-ex/0312023P. Christiansen Ph.D. Thesis, København’s Universitet

“Net” Proton= proton - antiproton dN/dy (5% central)

protons

antiprotons

net-proton


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BRAHMS

BRAHMS, submittedto PRL, nucl-ex/0312023P. Christiansen Ph.D. Thesis

AGS : high stoppingRHIC: more transparent

RHIC vs. AGS,SPS:


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BRAHMS

Calculate net-baryon distribution from net-protons (and y=0 yields of

, and Hijing…)

Net Baryon dN/dy


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BRAHMS

Gaussians in pz:

∑± ⎥

⎥⎦

⎤

⎢⎢⎣

⎡ ±− 2

2

2

))sinh((exp

pz

zN pym

σ =yδ 2.03 0.16

Rapidity loss: gaussian in pz

Rapidity loss:

∫ −−=−= py BB

partpp dy

dy

dNy

Nyyyy

0

)(2δ


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BRAHMS

=yδ 2.03 0.16

Rapidity loss: 6th order polynomial

Rapidity loss:

∫ −−=−= py BB

partpp dy

dy

dNy

Nyyyy

0

)(2δ

6 order polynomial

Gaussians in pz:

∑± ⎥

⎥⎦

⎤

⎢⎢⎣

⎡ ±− 2

2

2

))sinh((exp

pz

zN pym

σ

=yδ 2.00 0.10

∫−−p

p

y

y

BB

yT dyydy

dNm cosh)(

Total E=25.72.1TeV


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BRAHMS

y vs. ybeam

Even (unphysically) extreme approximations don’t change conclusions: scaling broken,large energy available

∫−−p

p

y

y

BB

yT dyydy

dNm cosh)(

Total E=25.72.1TeV


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BRAHMS

• Fit , K and p distributions (dN/dy and mT vs y) total energy of , K and p • Assume reasonable distribution for particles we don’t detect (0,n,…)• Calculate the total energy…

∑ ∫ ⎥⎦

⎤⎢⎣

⎡=

specieTtotal dy cosh(y)m

dydN E

NB: the method is verysensitive to the tails of the dN/dy dist. (10-15%) k+k-

pi+

pi-

pi0

lbar

k0bar

p

pbar

l

nbark0

n

?

35 TeV (EbeamNpart)of which 25 TeV are carried by produced particles.

p : 3108 p : 428K+ : 1628K- : 1093+: 5888- : 6117

0 : 6004n : 3729n : 513K0 : 1628K0 : 1093 : 1879 : 342

Energy (in GeV)

sum: 33.4 TeVproduced: 24.8TeV

Energy Balance…


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BRAHMS

Where is the energy?

≈9TeV in produced particlesin the covered y range-3<y<3


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BRAHMS

Strange to non-strange meson ratios

K-/-≈K+/+ at midrapidity

Depend strongly on baryochemical potential


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BRAHMS

Y < 1 : consistent with Hadron Gas Stat. ModelK+/+ : 15.6 0.1 % (stat)K/ : 14.7 0.1 % (stat) [Phys. Lett. B 518 (2001) 41]

Divergence at higher y :Associated K+ productionNo single source with

unique T and B

Strangeness with Kaons RAPIDITY DEPENDENCE

BRAHMS, PRL90 (2003) 102301

T~constant, B varies with y

Increasing y

63 GeV


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BRAHMSTop 5% central collisions

Kaon Spectra


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BRAHMS

Kaon Slopes Top 5% central collisions


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BRAHMS

Cover “peak” of strangematterhorn


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BRAHMS

Jets at RHIC

p+p jet+jet (STAR@RHIC)

Au+Au ??? (STAR@RHIC)

nucleon nucleonparton

jet

Find this……….in this

And, in BRAHMS, we only “see” this much…


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BRAHMS

η0 η22

Characterize “high” pT by single particle spectra


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BRAHMS

Nuclear Modification

Quantified by:

ηη

ddpNdN

ddpNdR

TNN

bin

TAB

AB /

/2

2

=

• Cronin Enhancement• Shadowing/Saturation• Jet-quenching

- yield relative to that fromN+N collisions, scaled forthe nuclear geometry (Nbin)

Jet-quenchingenergy loss of high momentum particles in the dense medium due to- gluon brehmstralung in the colored medium- hadronic multiple scattering

suppression of leading hadrons- Au+Au at sNN = 130GeV and 200GeV- next: energy+rapidity dependence


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BRAHMS

Arsene et al.PRL2003

To look at ‘only’ data, form ratio

Rη=Rcp(η=2.2)/Rcp(η=0)


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BRAHMS

d+Au Nuclear Modification η =0

High pT enhancement observed in d+Au collisionsat sNN=200 GeV.

Comparing Au+Au to d+Au strong effect of dense medium


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BRAHMS

submitted to PRLCronin enhancement at η=0- the “null” experiment that ruled out initial state effect as explanation for Au+Au suppressionIncreasing suppression for η3

- window to the low-x partons in the Au nuclei (QS~A1/3e-y)- consistent with CGC prediction

RdAu at sNN = 200 GeV


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BRAHMSone week of 62.4 GeV

running…New BRAHMS results

No RHIC p+p running at this energy:- what should we use as reference?


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BRAHMS

Nuclear modification factor RAuAu

- different centrality classesEnergy dependence (SPSRHIC) pT=3-4GeV/c

pT=3-4GeV/c40-60%20-40%10-20%0-10%

RAuAu at sNN = 62.4 GeV


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BRAHMS

Conclusions

High energy density 70% of energy

available for particle production

Source (nearly) same over >1 unit rapidity

63 GeV data: climb

the K/ “matterhorn”?

High pT suppression persists to high y in Au+Au

More saturation as y increases in d+Au

Gluon saturation describes data, though not uniquely

Lots left to do…


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BRAHMS

In ’BT’ (Danish morning tabloid)Feb. 2004

…….as plastic slippers with acrylic lining

?

That you can recreate the Big Bang in a particle accelerator

is simply a fantastic and earth shattering….

…discovery!

At the same level .....

brahms 22. oktober 2004 forward physics workshop, ku i.g.bearden, niels bohr institute 1 brahms...

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