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Transcript of BRAHMS 22. Oktober 2004 Forward Physics Workshop, KU I.G.Bearden, Niels Bohr Institute 1 BRAHMS...
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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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22. Oktober 2004 Forward Physics Workshop, KUI.G.Bearden, Niels Bohr Institute
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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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22. Oktober 2004 Forward Physics Workshop, KUI.G.Bearden, Niels Bohr Institute
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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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22. Oktober 2004 Forward Physics Workshop, KUI.G.Bearden, Niels Bohr Institute
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BRAHMS
K
p
BRAHMS Acceptance:
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22. Oktober 2004 Forward Physics Workshop, KUI.G.Bearden, Niels Bohr Institute
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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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22. Oktober 2004 Forward Physics Workshop, KUI.G.Bearden, Niels Bohr Institute
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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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22. Oktober 2004 Forward Physics Workshop, KUI.G.Bearden, Niels Bohr Institute
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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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22. Oktober 2004 Forward Physics Workshop, KUI.G.Bearden, Niels Bohr Institute
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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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22. Oktober 2004 Forward Physics Workshop, KUI.G.Bearden, Niels Bohr Institute
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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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22. Oktober 2004 Forward Physics Workshop, KUI.G.Bearden, Niels Bohr Institute
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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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22. Oktober 2004 Forward Physics Workshop, KUI.G.Bearden, Niels Bohr Institute
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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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22. Oktober 2004 Forward Physics Workshop, KUI.G.Bearden, Niels Bohr Institute
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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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22. Oktober 2004 Forward Physics Workshop, KUI.G.Bearden, Niels Bohr Institute
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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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22. Oktober 2004 Forward Physics Workshop, KUI.G.Bearden, Niels Bohr Institute
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BRAHMS
Where is the energy?
≈9TeV in produced particlesin the covered y range-3<y<3
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22. Oktober 2004 Forward Physics Workshop, KUI.G.Bearden, Niels Bohr Institute
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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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22. Oktober 2004 Forward Physics Workshop, KUI.G.Bearden, Niels Bohr Institute
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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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22. Oktober 2004 Forward Physics Workshop, KUI.G.Bearden, Niels Bohr Institute
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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 .....