Hadron performance in bes iii detector
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Hadron Performance in BES III detector. Ji X.B., Li G., Sun S.S., Wang L.L. IHEP Jan. 10 – 12, 2006. Outline. Reconstruction efficiency of hadron PID & its efficiency J/  physics ( ) Summary. All works are based on BOSS 5.0.0. Reconstruction efficiency.

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Hadron Performance in BES III detector

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Hadron performance in bes iii detector

Hadron Performance in BES III detector

Ji X.B., Li G., Sun S.S., Wang L.L.

IHEP

Jan. 10 – 12, 2006


Outline

Outline

  • Reconstruction efficiency of hadron

  • PID & its efficiency

  • J/ physics ( )

  • Summary

All works are based on BOSS 5.0.0

BES III meeting


Reconstruction efficiency

Reconstruction efficiency

  • is used to get the efficiency of proton, anti-proton and pion

  • is used to get the efficiency of pion and kaon and KS

  • is used to measure the soft pion efficiency

BES III meeting


Method

Method

  • Good hardron selection(Very loose cut criteria )

    Rxy < 1 cm, Z < 5 cm|cos\theta| < 0.93probPID > 0.001 (combined probability of dE/dx, TOF1, TOF2)

  • Event Selection At lease 3 particles should be reconstructed and identified

  • Efficiency

BES III meeting


Hadron performance in bes iii detector

Advantage:

  • Large Branch ratio (6.0  0.5)x 10-3

  • No neutral tracks

  • Momentum range is wide

  • Low background

    Total 50,000 MC events are used.

BES III meeting


Momentum distribution

Momentum distribution

pi

P

(0.0, 0.8)

Range: (0.0, 1.1)

BES III meeting


Missing mass

Missing mass

P

AP

-

+

BES III meeting


Match criteria

Match criteria

  • The missing direction |cos < 0.8|

  • The angle between the expected direction and the measured direction  < 15o

cos

BES III meeting


Distribution

 distribution

AP

P

+

-

BES III meeting


Hadron performance in bes iii detector

Reconstruction efficiency

P

AP

-

+

BES III meeting


Sun s s

(Sun S.S.)

  • 100,000 MC sample is used

  • is used to get the efficiency of pion and kaon

  • is used to get the efficiency of KS

BES III meeting


Missing mass1

Missing mass

mK2

m2

BES III meeting


Hadron performance in bes iii detector

Reconstruction efficiency

+

-

K+

K-

BES III meeting


Hadron performance in bes iii detector

Reconstruction efficiency of KS

mKs2

BES III meeting


Hadron performance in bes iii detector

(Li G.)

  • The decay mode of J/+- is used to reconstruct the J/ 

  • The particle with momentum less than 0.5 GeV/c is regarded as pion

BES III meeting


Hadron performance in bes iii detector

Tracking efficiency of pion

BES III meeting


Charged particle identification

Charged Particle Identification

  • Method:

     of dE/dx, Tof after reconstruction should obey standard normal distribution for a certain charged track:

    χdEdx=((dEdx)measured -(dEdx)exp)/(dEdx)exp

    χTof=((TOF)measured -(TOF)exp)/(TOF)exp

    So χ2= χ2dEdx+χ2TOF1+χ2TOF2

    (+χ2EMCE+χ2TOF1Q+……)

    should obey χ2distribution.

    We use quantity CL(χ2measured→+∞) of χ2distribution to identify charged particles.

BES III meeting


Charged particle identification1

Charged Particle Identification

  • Distribution of CL ( sample)

BES III meeting


Rec pid efficiency

Rec & PID efficiency( )

Prob>0.001

P

AP

-

+

BES III meeting


Rec pid efficiency1

Rec &PID efficiency( )

rec. only

rec. & PID

K-

K+

Prob>0.001

-

+

BES III meeting


Mc study of

J/ygpp

M=1859 MeV/c2

G < 30 MeV/c2 (90% CL)

0.2

0

0.1

0.3

M(pp)-2mp (GeV)

MC Study of .

  • Motivation

    • “Observation of a near-threshold enhancement in the ppbar mass spectrum from radiative J/ppbar decays” BES II, 2003

    • JPC maybe 0-+ or 0++

    • High precision measurement is important to determine the properties of the structure

BES III meeting


Mc study of1

MC Study of .

(Only very preliminary results)

  • The mainly background is

  • MC used(all generated by HOWL) :

BES III meeting


Event selection

Event Selection

  • Two good charged tracks with opposite charge

  • At least one good photon

  • Umiss < 0.02, Ptr < 0.001Umiss = Emiss – PmissPtr = 4Pmiss2sin2(/2)

BES III meeting


Hadron performance in bes iii detector

Umiss

Ptr

signal

background

BES III meeting


Hadron performance in bes iii detector

  • Normalized according to their Br

J/X

BES III meeting


Summary

Summary

  • The tracking efficiency and PID efficiency of hardrons are measured from different decay modes

  • A rough estimation of proton anti-proton threshold enhancement

  • Many works should be done in the future

BES III meeting


Hadron performance in bes iii detector

Thank You!

BES III meeting


Rec and pid

Rec and PID

BES III meeting


Hadron performance in bes iii detector

1M

BES III meeting


Different pid

Different pid

BES III meeting


Hadron performance in bes iii detector

Chi

BES III meeting


Angle

angle

BES III meeting


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