Yuji Tsuchimoto

1
Measurement of f mesonat sNN200GeV dAu
collision in PHENIX

• ?? ??
• Yuji Tsuchimoto
• for PHENIX collaboration
• tsuchi_at_hepl.hiroshima-u.ac.jp
• Experimental Quark Physics group,
• Department of Physics,
• Hiroshima University, Japan

• Contents
• Motivation
• event selection / electron ID
• Invariant mass spectra

2
Motivation
Quark mass in vacuum mu md 5 MeV/c2 ms 100
MeV/c2
(partial) chiral symmetry breaking
Effective quark mass in hadron mu md 300
MeV/c2 ms 500 MeV/c2
T.Hatsuda and S.Lee QCD sum rules for vector
mesons in the nuclear medium (Phys.Rev.C46-1
1992)

• The chiral symmetry is partially restored at
  normal nuclear density.
• Mass modification of vector mesons is expected.

3
precede experiments

• Vector meson mass may be modified in dense
  matter.
• What happened at RHIC?

KEK E325
CERN CERES
G. Agakishiev et al. Low-mass ee- pair
production in 158A GeV Pb-Au collisions at the
CERN SPS, its dependence on multiplicity and
transverse Momentum (Phys.Lett.B422405-412,1998 )
K.Ozawa et al. Observation of r/v Meson
Modification in Nuclear Matter (Phys.Rev.Lett
86-22)
4
low-mass mesons

• w mass 782 MeV/c2, G 8.4 MeV/c2
• Mass modification will be larger than f.
• f mass 1019 MeV/c2, G 4.2 MeV/c2
• Branching ratio of f?KK to f?ee- is sensitive to
  mass modification.

5
PHENIX detector

• RHIC pp, dAu, AuAu sNN 200GeV (500GeV
  for pp)

• BBC ? trigger
• PHENIX Central Arms can detect electrons,
  photons, hadrons within the same h region, h lt
  0.35
• Drift/Pad Chamber ? track curvature ? momentum
• EMC ? energy
• RICH ? electron ID

6
Electron Identification

• Request as electrons are
• Num of hit PMT in RICH 2
• Ring shape (c2/DoF lt 15 )
• Reject high pT p
• 0.6 lt Ee/e-/p lt 1.5
• Track matching lt 3s

7
ERT electron trigger Event selection
Minimum bias

• Front-end electronics and data storage limit
  trigger and recording rate.
• Give priority for electron events to record.
• ERT electron trigger by RICH EMC online

ERT triggered

• Analyzed 7.5M of ERT-electron Triggered Events.
• Corresponds to 437M minimum bias (raw trigger)
• 10 of total data taken during run3

8
Invariant Mass Spectra
Photon Conversion
w
f
30 of J/y

• Background estimated by event mixing with offline
  ERT-electron trigger emulation
• Use like-sign pair spectra for BG normalization.
• 400MeV/c lt Momentum lt 5GeV/c

9
Invariant Mass Spectralow mass meson region
w
f

• Shown data is 10 of total taken data.

10
Summary next step

• I studied w and f mesons measurement in ee- pair
  at dAu collisions.
• PHENIX has capability to measure w and f mesons
  by ee-.
• I will show full-statistics results at next JPS.
• Acceptance correction
• Compare with f?KK result
• Compare with AuAu run

11
Back Up Slides
12
f to ee- at AuAu (run2)
PHENIX preliminary

• Mass peak and width agree within errors of PDG
  values

13
BG Normalization using like-sign mass spectra

• Make like-sign pair spectra for normalization.
• Same normalization factor was used on
  like-/unlike-sign.