Current status of estimation of Eγ resolution 12/19(Tue) analysis meeting Y.Kato

To know the Eγ resolution is equal to know the momentum resolution! Strategy If reaction is assumed, Eγ is calculated analytically from measured momentum. In the case of γ p →　k+ Λ(1116), To know the Eγ resolution is equal to know the momentum resolution!

LLH2 run25452-25968 Analyzed data …LLH2 run23690-24058 Situation is different in these runs. →later

・σfromΔp is estimated from MC. γ　p → k+ Λ(1116) γ　p → π+ π- p ΔEγ(GeV) Momentum of k+(GeV/c) Eγ(GeV) ・σfromΔp is estimated from MC. ・vertex,decay-in-flight,chi2probability,ybar cut is included. It is neccesary to investigate momentum resolution of MC and real data is differnte or not.

→ MC γ p →k+ Λ(1116)→k+ p pi- Real data γ(p,p pi-)X line+gauss fit Check the invariant mass of real data and MC γ p →k+ Λ(1116)→k+ p pi-　 Real data line+gauss fit → 3sigma cut is applied M(ppi-) γ(p,p pi-)X σ=1.30±0.03MeV MC σ=1.24MeV

Smear the momentum resolution of MC If ΔEγ is assumed , momentum resolution of real data can be obtained from missing mass. ΔEγ is assumed to be 12MeV MC black:Real data Red :MC smear ΔP(GeV/c) σ=1.31MeV Pk+(GeV/c)

γ p → k+ Λ(1116) ΔE after smear of MC for various mode Red: Before smear black: after smear ΔEγ Eγ（GeV） Fit by constant value→11.9MeV±0.1

γ p →　pi+ pi- p Red: Before smear black: after smear ΔEγ=11.8MeV±0.1

γ p →　k+ k- p Red: Before smear black: after smear ΔEγ=10.7MeV±0.3

The hint for the reason of inconsistency between real data and MC number of hits used in the tracking Real data MC number of hits removed in the tracking

γ p →k+ Λ(1116) Red: nhits<16 Black: nhits>=16 ΔEγ(GeV) Pk+(GeV/c)

Run dependence γp → k+ Λ γp → π+ π- p run23690-24058 run23690-24058 pk+(GeV/c) Eγ change of ΔEγ or Δp ?

check the invariant mass run25452-25968 run23690-24058 σ=1.30±0.03MeV σ=1.26±0.04MeV

How large invariant mass change if run dependence of missing-mass is all due to the change of momentum resolution? smear to adjust run23690-24058 smear to adjust run25452-25968 σ=1.31MeV σ=1.47MeV

γp→pi+pi-p vty(mm) VTY dependence run23690-24058 run25452-25968 black: 23690-24058 Red: 25452-25968 γp→pi+pi-p ΔE(GeV) vty(mm)

Summary ・Validity of momentum resolution in MC is essential to determine Eγ resolution. ・Invariant mass study indicates momentum resolution is under estimated in MC. ・Simple smearing makes inconsistency. ・Number of hits is different in real data and MC ・Run dependence of missing mass resolution can’t explain by the change of momentum resolution.