Update of Analysis ~LEPS Collaboration Meeting in Taiwan

Nuclear Physics Group, Academia Sinica

Bo-Ru, Lin2006/01/12

Outline

Φphotoproduction using LD2 target Validity of momentum calculation Determination of Eγ smearing Determination of Appropriate mass offshell effect t-resolution dN/dt fitting Background estimation

Φ-photoproduction using LD2 target.

p, n, or D ?

• Incoherent Interaction ： Photon interact with constituent nucleon, which is proton or neutron.• Coherent Interaction ： Photon interact with deuteron as a whole.

Isospin effect in Coherent production

η: isoscalar

π: isovector

D : isoscalar

: isoscalar

Allowed

Forbidden

By isospin conservation we should be able to separate π from the whole exchanging channels.

Conjecture ：

Pseudo-scalar Exchange

MMd of LD2, and LH2Missing mass distributions provide us a tool.

22 )()( PPEmEMM dd

LD2 LH2

Validity of momentum Calculation

Accredited Md = 1.875 GeV Accredited MΛ = 1.520 GeV

Validity of momentum Calculation

Accredited Mp = 0.938 GeV

Validity of momentum Calculation

Accredited MΦ = 0.938 GeV

Determination of appropriate MC Eγ smearing

15 Mev Smearing

MMp fitting of LH2 real data using different Eγ smearing

Determination of appropriate Eγ smearing

10 Mev SmearingTwo component (11.64 MeV)

Smearing

Determination of Appropriate mass offshell effect

Use MC Incoherent MMd fit LD2 MMd (in the region 1.9~2.1)

Do subtraction and fit with gaussian distribution. Compare the result with coherent distribution

Determination of Appropriate mass offshell effect

Determination of Appropriate mass offshell effect

Determination of Appropriate mass offshell effect

t - resolution ~ sigma plot

The t-resolution is better than 0.02 GeV

Fit (t-in) – (t-out) with gaussian distribution to get σ value

t-in : from event generator

t-out : deduced in the way the same as real data

MMd Fitting to Separate Coherent from Incoherent events

Fitting of MMd of LD2 real data using Mote-Carlo generated incoherent, coherent events.

coherent

incoherent

sum

Cross check of MMd, and MMp Fitting

MMd

MMp

Coherent LD2 dN/dt Fitting

min||exp||min

ttbttdt

d

dt

d

Fitting Formula ：

min||exp||min

ttbttdt

d

dt

d

||minttdt

d

b

intercept

slope

Coherent LD2 dN/dt Fitting

t bin : 30 MeV

t bin : 20 MeV

t bin : 40 MeV

Coherent LD2 Common slope dN/dt Fitting

t bin : 30 MeV

t bin : 20 MeV

t bin : 40 MeV

Slope : 20~23

Slope with last Eγbin removed : 17 ~19

Incoherent LD2 dN/dt Fitting

Incoherent LD2 Common slope dN/dt Fitting

dN/dt Fitting of coherent, incoherent, LH2 results

LH2

Incoherent

Coherent

Coherent Slope : ~18.5

Incoherent Slope : ~4.0

LH2 Slope : ~3.6

Background Estimation

10 Mev cut

MC Backgrounds

None-resonant KKn

Λ(1520)

None-resonant KKd

Invm-kk MMpMMd

Multidimensional Fitting

Invm-KK MMd MMp

LD2 Data

Incoherent

Coherent

Sum of all

Fit invm-KK, MMd, MMp simultaneously without background.

Multidimensional Fitting

Invm-KK MMd MMp

LD2 Data

Incoherent

Coherent

Sum of BG

Sum of all

KKd

Sum of BG

Λ(1520)

KKn

Multidimensional Fitting

Invm-KK MMd MMp

LD2 Data

Incoherent

Coherent

Sum of BG

Sum of all

Next step : Apply the same procedure with t-binning

Brief Summary

Stable results of preliminary dN/dt analysis are acquired.

Background estimation in every t, Eγ bin to acquire pure Φ events.

Thank you for paying attention

Backup Slides

MMd

MMd, using smaller binning

Determination of Appropriate mass offshell effect ~ Results of other Ntuples

Determination of Appropriate mass offshell effect ~ Results of other Ntuples

Determination of Appropriate mass offshell effect ~ Results of other Ntuples

Determination of Appropriate mass offshell effect ~ Results of other Ntuples

Determination of Appropriate mass offshell effect ~ Results of other Ntuples