Measurement of single muons with the PHENIX experiment at RHIC

1
Measurement of single muons with the PHENIX
experiment at RHIC
Hot Quarks 2006, May 20
D.J Kim Yonsei University For the PHENIX
Collaboration
2
Outline

• Introduction
• How can we measure HF ?
• Background measurements to the cocktails (
  1.Free DecayK,p, 2.Punch-through )
• Prompt muon results in pp. dAu
• Light meson bg measurement in CuCu
• Summary and Outlook

3
Physics Motivations

• Why do we measure heavy quarks (charm/bottom)?
• In pp collisions
• Important test of pQCD. Can pQCD predict charm
  production( LO, NLO )?
• Base line analysis for dAu and AuAu
• In dAu collisions
• Study of cold nuclear matter effect (Gluon
  Saturation/CGC,shadowing , Cronin effect)
• In AA collisions
• Medium modification effects (energy loss,
  collective flow)
• Important baseline of J/? analysis

4
Charm energy loss in AuAu 200GeV at y0

• Even heavy quark (charm) suffers substantial
  energy loss in the matter
• The data provides a strong constraint on the
  energy loss models.
• Charm/Bottom contribution ?
• Radiative energy loss Elastic energy loss with
  Different as .3 or .43
• (M. G. Mustafa, Phys.Rev.C72014905,2005)
• Teaney and Moore (hep-ph/0412346)
• K.J Eskola (Nucl.Phys.A747(2005) 511)
• Systematics
• Large in low pT because of low S/B
• At higher pT, systematic error
• statistical error
• Uncertainty in pp is large
• preparing the high pT RAA (up to pT 10 GeV/c).
• Run5 pp ( x 10 stat )

(1-3) from N. Armesto, et al., hep-ph/0501225 (4)
from M. Djordjevic, M. Gyulassy, S.Wicks, Phys.
Rev. Lett. 94, 112301
5
How to measure Heavy Flavor ?

• Experimentally observe the decay products of
  Heavy Flavor particles (e.g. D-mesons)
• Hadronic decay channels D?Kp, D0?p p- p0
• Semi-leptonic decays D?e(m) K ne

• STAR
• Direct D mesons hadronic decay channels in dAu
• D0?Kp
• D?Kpp
• D?D0 p
• Single electron measurements in pp, dAu

• PHENIX
• Single electron measurements in pp, dAu, AuAu
  , y0?sNN 130,200,62.4 GeV
• Single muon measurements
• in pp, dAu ,1
• ?sNN 200 GeV

6
What have we measured

• Open heavy flavor (HF)
• y, pT dependence ?(y0,pp,dAu,AuAu,
  y1.65,pp,dAu)
• Centrality dependence ?(y0,dAu,AuAu)
• Reaction plane dependence ?(y0, AuAu)
• RHIC provided CuCu 200GeV(3.0 nb-1),
  62.4GeV(0.19 nb-1) Collisions during 2005
• Better systematic studies are possible with
  different vs, collision species.
• better precision on the centrality measurement
  in the lower Npart region

Species pp, dAu, CuCu, AuAu vs 200 GeV,
62.4GeV, 130GeV Statistics More is always
better (allows reduction in statistical and
systematic errors)
7
PHENIX detector at RHIC

• Electron measurements
• h
• Two separate arms 2xDf 900
• dp/p 1 p
• Electron ID
• RICH (gthr35)
• e/p separation up to pT 4.8 GeV/c
• Muon measurements
• 1.2
• Two separate arms in forward and backward
  rapidity

8
Muon Production origin of muons

• Origins of muons
• PYTHIA pp _at_ vs200GeV
• low PT
• light hadron decays
• high PT
• Heavy quark decays

Muon PT distribution
9
Candidate Muon Tracks in the Muon Spectrometer
The muon arms covered rapidities 1.2 Candidate Tracks
Prompt Muons
Punch-through hadrons
Stopped hadrons
Decay muons
10
Decay muon Contribution(N_decay)
The yield of decay muons depends on the collision
location linearly, which also constrains the
hadron production, I hadron , at the collision
point.
11
Punch-Through hadrons ( N_punch)

• Extract decay component from z-vertex slope of
  normalized muon yield.
• Calculate punch-through component with simplified
  absorption model

Nuclear interaction length ?

• Nuclear interaction cross section
• not well-known
• can be resolved with large statistics run5pp,
  CuCu with this method!!

12
Cocktails

• Sources of ? candidates
• Decay ? is important at all pT.
• Punch-through is small, but
• important due to large uncertainty.
• Prompt ? signal comparable to decay
• ? when pT 2(GeV/c).

13
Comparison to Theory pp 200GeV
FONLL Fixed Order next-to-leading order terms
and Next-to-Leading-Log large pT resummation.

• PYTHIA 6.205 parameters, tuned to describe
  existing ?s
• ( PDF CTEQ5L, mC 1.25 GeV, mB 4.1 GeV,
• 1.5 GeV, K 3.5 )

We see excess over NLO calculation. The excess
gets even stronger at forward, possibly due to
the rapidity dependence of cross section.
Total cross section for PYTHIA 6.205 ?CC 0.658
mb, ?BB 3.77 ?b
14
PHENIX muon arms x coverage
Particle production in the d direction (north) is
sensitive to the small-x parton distribution in
the Au nuclei whereas in the gold (south) is
sensitive to the large-x in Au
15
Prompt ?s pT spectra in dAu collisions and RdAu
North Arm d going direction South Arm Au going
direction

• For muons from open heavy flavor decay, a
  suppression in forward rapidity is observed. It
  is consistent with CGC. Results are statistically
  limited.
• The mechanism of the observed enhancement at
  backward rapidity needs more theoretical
  investigation. Anti-shadowing and recombination
  could lead to such enhancement ?

16
Decay muons ( pT) in CuCu 200GeV
200GeV pp
200GeV CuCu
PHENIX preliminary

• consistent with run2 pp
• MinBias pT spectra in CuCu 200GeV only at this
  moment(Online production)
• Limited statistics now, Full data set will be
  available in the near future
• CuCu 200GeV statistics x10 more

17
Nuclear Modification Factor CuCu 200GeV

• shows enhancement in higher pT in the forward
  rapidity
• it is consistent with the mid-rapidity
  measurement within the errors
• One of main physical background to Inclusive
  muons is under control

18
Rapidity

• Modest Gaussian Shape is observed
• pT1GeV/c in MinBias collisions

19
Summary pp, dAu

• FONLL and PYTHIA 6.205 under predicted prompt ?
  at forward rapidity in pp collisions at 200 GeV.
• For muons from open heavy flavor decay, a
  suppression in forward rapidity is observed. It
  is consistent with CGC. Results are statistically
  limited.
• The mechanism of the observed enhancement at
  backward rapidity needs more theoretical
  investigation. Anti-shadowing and recombination
  could lead to such enhancement.
• Both Muon from light meson decay and heavy flavor
  decay show same behavior at forward and backward
  direction in dAu collisions.

20
Perspective

• Non-photonic Single electron RAA in AuAu 200GeV
  collisions suggests that
• Even heavy quark suffers substantial energy loss
  in the matter
• Still systematical errors and statistical error
  is not sufficient to constraint
• energy loss models ? Can be improved with
  better pp reference and more high pT data points
  AND.
• More systematic studies can be possible via
  different collision species, energies (CuCu
  200GeV, 62.4GeV), and rapidities.
• stage is set, background analysis are underway
• Light meson pT and RAA in CuCu MB 200GeV
  collisions are measured at this moment in the
  forward rapidity.
• punch-through hadrons can be calibrated with
  large set of tracks ( run5pp,CuCu ) with great
  precision
• Perspectives on CuCu 200GeV , 62.4GeV
• Light mesons centrality dependency
• can be studied with good statistics
• Prompt muon signal ( charm, bottom )
• Flow

21
RHIC History
X 25
22
Comparison Prompt ?- pt spectrum with theory
Run2pp ?- FONLL Solid line and band Without
scaling the charm contribution dotted line
FONLL Fixed Order next-to-leading order terms
and Next-to-Leading-Log large pT resummation.
FONLL and PYTHIA calculation under predicted
PHENIX Data at forward rapidity,
23
Theory Comparison
M. Djordjevic, M. Gyulassy, S.Wicks, Phys. Rev.
Lett. 94, 112301
Disagreement with PHENIX preliminary data!
24
How can we solve the problem?
N. Armesto et al., Phys. Rev. D 71, 054027 (2005)
Reasonable agreement, but the dNg/dy3500 is not
physical!
25
Elastic Energy loss ?
First results indicate that the elastic energy
loss may be important M. G. Mustafa,
Phys.Rev.C72014905,2005
as .3

• Electrons

• Pions

26
as .3
as .4
27
(No Transcript)
28
(No Transcript)
29
(No Transcript)
30
(No Transcript)
31
(No Transcript)