槌本 裕二Yuji Tsuchimoto

tsuchimoto@bnl.gov

High-energy Hadron Physics group,Department of Physics,

Hiroshima University, Japan

meson productionin =200 GeV proton+proton

collisions at PHENIXs

Why am I interested in

• Chiral symmetry• Lagrangean in the Normal QCD Vacuum

– Mass breaks chiral symmetry

• Where chiral symmetry restored– Immediately after Big Bang– Core of neutron star– Heavy Ion Collision

MGGDiL aa

4

1

5ie

密度

温度

初期

宇宙

中性子星ハドロン相

Heavy Ion Collision

Chiral symmetry phase

Hadron phaseneutron

star

density

tem

pera

ture

spac

e

z

t

Time expansion

• Observable– Mass– Lifetime– Yield– Branching ratio

Thermal equilibrium ~10fm/c

meson lifetime~44fm/c_

ss

Au Au p p

Au Au pp

→K+K-

(49%)

→e+e-

(0.3%)

K+

K-

e+

e-

e+

e-

K+

K-

In medium

Pre-thermal equilibrium ~1fm/c

z

t

PHENIX

Central Arms completed in Run 2• can detect electrons, photons, hadrons• || < 0.35 and pT > 0.2 GeV/c

•Drift Chamber → track curvature → momentum•EMC & TOF → Time of Flight → mass

•EMC : High Acceptance, low resolution•TOF : High resolution, low acceptance

Kaon Identification

• Momentum/charge from track curvature measured by Drift chamber• Kaon < ± 2Pion > ± 5for EMC/ToF• |Z vertex| < 30cm• ( DC Quality 63|31 & EMC/ToF Matching < 2

K = ±2

= ± 5

Momentum/charge [GeV/c] Momentum/charge [GeV/c]

Mas

s(E

MC

)[G

eV/c

2 ]

• Mass measured DC and ToF hit timing and path length• Yellow region = Kaon < ±2p<1 GeV/c)

Kaon Identification (cont.)

pK

Mass measured by DC & TOF

Mass [GeV/c2]

Invariant Mass and Background EstimationBackground estimation

Event mixing of K+ and K

Z vertex|<5cm && number of K >= 2 , in the same runScaled as equal number between 1.1 and 1.2 GeV/c2

Invariant mass [GeV/c2]

Invariant Mass After Background Subtraction

]2

invariant mass [GeV/c-K+K1 1.01 1.02 1.03 1.04

-2

0

2

4

6

8

10

12

invariant mass distribution-K+Background subtructed K HsubNent = 342Mean = 1.022RMS = 0.01095

invariant mass distribution-K+Background subtructed K Hsub

]2

invariant mass [GeV/c-K+K1 1.01 1.02 1.03 1.04

-5

0

5

10

15

invariant mass distribution-K+Background subtructed K HsubNent = 1895Mean = 1.024RMS = 0.01273

invariant mass distribution-K+Background subtructed K Hsub

]2

invariant mass [GeV/c-K+K1 1.01 1.02 1.03 1.04

-4

-2

0

2

4

6

8

10

12

invariant mass distribution-K+Background subtructed K HsubNent = 840Mean = 1.022RMS = 0.01137

invariant mass distribution-K+Background subtructed K Hsub

Invariant mass ofK+K- by TOF

Invariant mass [GeV/c2]

Mean 1018.8±0.6 MeV/c2 Sigma 2.8±0.4 MeV/c2Fit function : Gaussian

Mean and width error are only fitting error

East EMC Mean 1017.8±1.3 MeV/c2 Sigma 4.2±1.3 MeV/c2 Mean 1019.8±1.1 MeV/c2

Sigma 3.4±0.9 MeV/c2West EMC

counter mean[MeV] width[MeV]

ToF 1018.8±0.6 2.8±0.4

EMC-E 1017.8±1.3 4.2±1.3

EMC-W 1019.8±1.1 3.4±0.9

Acceptance Correction

• Estimate ratio of measured to thrown – Low momentum kaon do

es not reach to tracking detectors due to small spiral

– No detector

• PID cut efficiency– High momentum kaon is r

ejected doe to in 5 sigma of candidate

Conditions of the Simulation• Only single in each event• || < 0.6 (flat)• |Z| < 30cm (flat)

• 0 < pT < 10 GeV/c (flat)

• All decay to K+K- only in this simulation• 0<<2 (flat)• 1.0M events• Binning by transverse mass

22222TyxT pmppmm

Weighted by initial pT of

• pT distribution of initial phi which I used was flat distribution. It may cause a few % overestimation of efficiency

• I weighted by exponential function of w(mT)~exp(-mT/T) initial mT when I fill the histogram. This slope is as same as the slope of results ( iterative )

]2

[GeV/cf

-mTm0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2 2.2 2.4

10-5

10-4

10-3

10-2

10-1

1

10

102

103

distributionTSimulation m pisaNent = 9820094Mean = 0.4376RMS = 0.4069

distributionTSimulation m

Weighted Thrown

Weighted detected

Yield (EMC vs TOF)

• Minimum bias triggered• |z|<30cm• Detector dead-map is not applied completely yet

]2[Ge V/c-mTm0 0.4 0.8 1.2 1.6 2 2.4

dN

Te

vt

dm

d

N/d

10-5

10-4

10-3

10-2

ToF

EMC-W

EMC-E

Arb

itrar

y U

nit

Summary• Consistent mass and width within 1• Consistent slopes of mT distribution

were obtained by DC, ToF and EMC hit

• Apply detector dead-map

• Calculate cross section of pp→+X

• I’m interested in Run3 → KK and ee

Next step