Λ *(1520) photoproduction from lh 2 and ld 2

2008.5.1 LEPS Collaboration Meeting In Taiwan

Λ*(1520) Photoproductionfrom LH2 and LD2

Jia-Ye Chen

Outline

Physics Motivation Previous Results : LAMP2 and CLAS Data Analysis

Reaction Channels Analysis Scenarios Event Selections Λ*(1520) production in Kp and KK detection modes Background Linearity K- decay asymmetry in Λ*(1520) Helicity frame

• Side-Band Subtraction• Monte Carlo Background Fitting (By Muramatsu-san)

Total Cross Section of LH2 and LD2

Summary

)( 23 PJ

)( 21 PJ

)1( PJ)0( PJ

)1(* PJK

)0( PJK

Physics Motivation

K2sin

K

2cos3

1

Helicity Frame

γγ ＋ ＋ p → Kp → K++ + + Λ*(1520) Λ*(1520) →→ KK++ + + pp + + KK--

exchangeK

mz

21

exchangeK

mz

*

23

1. If ONLY spinless kaon, K-, exchange → 021

23

z

z

m

m

1

3

21

23

z

z

m

m2. If ONLY vector kaon, K*- ,exchange → (If solely determined by Clebsch-Gordon coefficients)

Previous Results

KKKf 22 sincos

3

1)(

1

1

1cos)( dfKAssume

75.0

CLASElectroproduction

LAMP2Photoproduction

Contribution

Q2≠0

Reaction Channels

pKKKpd *)(

Background Channels

KpKnd *

pKKKp *

pKKpp pKKp

Production Channels

NKKNN

LH2

LD2

LH2

LD2 KpKnd *0)(

Analysis ScenariosSide-Band Subtraction Monte Carlo Background Fitting

Assuming that the background linearity is good, , the count in S0 region can be obtained accompany with the sneak-in factor from Monte Carlo simulation.

0)( 2121

0 BBB

2121

02121

0

212121

00 )()(

BBBSSS

BBSSBS

Subtracting the background components from real data mass spectrum to get the count of Λ*(1520).

Event Selections

Kp mode ntrk > 1 3 sigma PID ikm/ipr ≠ 0 ithtofhit(ikm/ipr) > 0 prbchi2(ikm/ipr) ≥ 0.02 abs(ytof(ikm/ipr)-tofdiff(ikm/ipr)) ≤ 80 abs(itof(ikm/ipr)-tofid(ikm/ipr)) < 2 noutl(ikm/ipr) ≤ 6 -1100 ≤ vtz ≤ -900 abs(vtx) ≤ 15 0.40 ≤ missing mass of pK- ≤ 0.62 GeV photon energy ≥ 1.75 GeV abs(missing mass of proton – 1.020) > 15

MeV

KK mode ntrk > 1 4 sigma PID ikm/ikp ≠ 0 ithtofhit(ikm/ikp) > 0 prbchi2(ikm/ikp) ≥ 0.02 abs(ytof(ikm/ikp)-tofdiff(ikm/ikp)) ≤ 80 abs(itof(ikm/ikp)-tofid(ikm/ikp)) < 2 noutl(ikm/ikp) ≤ 6 -1100 ≤ vtz ≤ -900 abs(vtx) ≤ 25 abs(missing mass of proton – Mp) < 0.050

GeV photon energy ≥ 2.00 GeV abs(invm(KpKm) – 1.020) > 10 MeV

KP Mode : LH2

KP Mode : LD2

Background Estimation How-to

1. Generating known reaction components individually.

2. To select 2 detected particles (K-p or K+K-) reconstructed at the forward spectrometer.

3. Skimming each component with kinematics filters.

4. Fitting all components with real data spectrum in various dependence simultaneously to obtain the scaling parameters.

Monte Carlo Fitting : LH2 (Kp Mode)

Monte Carlo Fitting : LD2 (Kp Mode)

KP Mode : LH2

KP Mode : LD2

KK Mode : LH2

Monte Carlo Fitting : LH2 (KK)

KK Mode : LH2

Background Linearity How-to

0

210

)2,1,0()2,1,0()2,1,0(

)2,1,0()2,1,0()2,1,0(

0

210

))()(()(

)(

22212

22

21

B

BBB

L

KKpBBB

KKpBBB

B

BBB

N

ErrorErrorErrorError

RNRNError

RNRNN

N

NNNLLinearity

KKp

KKp

Global Fitting Factors

KKp = 0.0282

KL* = 0.0171

phi = 0.0361

Global Fitting Factors

KKp = 0.0282

KL* = 0.0171

phi = 0.0361

Relative Ratios

RKKp = 1.

RL* = 0.60638

Rphi = 1.28014

Linearity by Photon Energy

Kp

K? exchange5 Energy Slices

LH2(Kp vs KK)

Contribution

1. Both in the Kp(LH2 & LD2) and KK(LH2) detection mode, the results between side-band subtraction and Monte Carlo fitting are consistent.

2. In the Kp detection mode, there is an energy dependence on the K* exchange in LH2

case; however, no obvious energy dependence in LD2 case.

3. The results between from Kp and KK detection mode are compatible in higher photon energy region, even if the statistics is lower in KK detection mode.

5 SlicesLH2

5 SlicesLD2

5 SlicesLH2(KK)

Comparison betweenLAMP2, CLAS and LEPS

Total Cross Section

*0 Kn* Kp

S.-II Nam, A. Hosaka and H.-C. Kim, Phys. Rev. D 71, 114012.

The contact term is absent, since the process γ+n→K0Λ* is the neutral one. Its absence cause the total cross section to become much smaller than that for the proton target.

PRELIMINARY

PRELIMINARY

Eγ NYieldAcceptanc

eNγ

1.75-1.85

57 0.01202.421E+

11

1.85-1.95

83 0.01152.7095E

+11

1.95-2.05

99 0.01173.0042E

+11

2.05-2.10

47 0.01241.6071E

+11

2.10-2.15

44 0.01271.6187E

+11

2.15-2.20

47 0.01301.8283E

+11

2.20-2.25

40 0.01371.876E+

11

2.25-2.30

47 0.01401.862E+

11

2.30-2.35

46 0.01471.8304E

+11

2.35-2.40

11 0.01581.9476E

+11

Eγ NYieldAcceptanc

eNγ

1.75-1.85

121 0.01043.5112E

+11

1.85-1.95

182 0.01144.1133E

+11

1.95-2.05

209 0.01194.9196E

+11

2.05-2.10

97 0.01222.5873E

+11

2.10-2.15

116 0.01212.6265E

+11

2.15-2.20

103 0.01292.959E+

11

2.20-2.25

93 0.01303.0304E

+11

2.25-2.30

110 0.01342.9449E

+11

2.30-2.35

82 0.01382.9198E

+11

2.35-2.40

78 0.01483.0008E

+11

bcm

cmg

ett cmNLH

17123

23

arg2

1076574.61076574.6

00794.1

1002.60708.016:

2

3

LH2 LD2

bcm

cmg

ett cmNLD

17123

23

arg2

1013904.81013904.8

01355.2

1002.6169.016:

2

3

225.0

762.0

52.0

*

1

pK

ntag

trans

BR

P

P

BRPPNNAccNb ntagtransettphotonYield 1arg/Nγ : /np1b/v01/sp8lep/OfficialMacro/runinfo/Photo_llh(d)2.dat by Sumihama-san

Summary In the study of K- decay asymmetry in Λ* helicity frame, if the background linearit

y is reasonable, the consistency between side-band subtraction and Monte Carlo fitting is good.

Without phi exclusion cut, it is very difficult to study in the KK detection mode; in the Kp detection mode, however, there is no significant difference between the results with and without phi exclusion cut in decay asymmetry study. The results between from Kp and KK detection mode are compatible in higher photon energy region, even if the statistics is lower in KK detection mode.

To make a comparison between different targets, LH2 and LD2, in Kp detection mode, no obvious photon energy dependence was observed in LD2 data. This difference might come from the Λ* photoproduction of neutron.

In Λ* photoproduction, the dominance of K* exchange is proportional to photon energy; in the low energy region, K exchange become important and the contribution from K and K* exchange are equivalent. From our result, it provides a nice bridge between LAMP2 and CLAS experiment, in the high energy, K* exchange significantly dominate the Λ* photoproduction. (Clebsch-Gordon coefficients)

Refer to “Phys. Rev. D 71, 114012“, the absence of the contact term in neutron process leads to the total cross section to become much smaller than that for the proton target. Therefore, from our result, the total cross section of neutron is small, but, not as small as the theoretical prediction, 1/30. On the other hand, our result are not consistent with the theoretical prediction, it is about a factor of 2.

2008.5.1 LEPS Collaboration Meeting In Taiwan

Backup Slices

Photon Energy SpectrumLH2(Kp) LH2(KK)

LD2(Kp) LD2(KK)

KK Mode : LD2

KK Mode : LD2

KK Mode (W/O Phi exclusion Cut)

KK Mode (W/O Phi exclusion Cut)

KK Mode (W/O Phi exclusion Cut)

Full Photon Energy

LH2(Kp vs KK)

2 Energy Slices

LH2(Kp vs KK)

3 Energy Slices

LH2(Kp vs KK)

4 Energy Slices

LH2(Kp vs KK)

Full Photon Energy

2 Slices : LH2(Kp)

2 Slices : LD2(Kp)

2 Slices : LH2(KK)

3 Slices : LH2(Kp)

3 Slices : LD2(Kp)

3 Slices : LH2(KK)

4 Slices : LH2(Kp)

4 Slices : LD2(Kp)

4 Slices : LH2(KK)