HES HKS meeting

8 Oct 2010T.Gogami

Contents

• H2O Missing mass– tracking code

• POSITRON simulation

Missing Mass (H2O)From Shichijo’s ppt

Λ

Acc. background

Debug

• +1• - +

48% up

52Cr CH2

16% up40% up

H2O target

H2O

CUTH2O target missing mass

OLD NEW

•Number of event •S/N

Tracking code Tracking codeΛ Λ

HES χ2 < 300HKS χ2 < 300

Ratio of number of Λ event

• HES χ2 < 50 (Fixed)• HKS χ2 < x

Much more event

Simulationfor positron at target

e- ( 2.344 [GeV] )

Target

Virtual detector(4cm×4cm )

Thickness 1 [μm]

0.5 [cm]

POSITRON• Number• Angular distribution• Energy distribution

20000 events

Angular distribution of e+

• event : e+ = 100k : 1

• 8 [μA] = 5×1013

• Rate of e+

= 5×108 [Hz]= 500 [MHz]

52Cr target

SIMULATION

Generated 100M eventsHKS detect θ > 1°e+ generated in target should not be accepted in HKS==>Background in HKS has other root

Summary and to do• Summary– Tracking code modification

• Lambda event up (H2O target)

– Simulation around target• positron angular distribution

– e+ generated in target should not be accepted in HKS

• to do– Tracking code

• background reject routine– POSITRON

• Around target – H20 target model

• Hall prove entrance• Real data

– ADC

100 M electron on target (52Cr)[rad]

•e+

•Momentum > 800 [MeV]

Angular distribution of e+

12C target

SIMULATION

Pb

e,e+ b.g. in HKSTOP view

Side view

X [cm]

X’ [r

ad]

5 × 5 [cm2]

HKS - DHKS - Q

B.G mix rate in HKS trigger

just after pattern recognition==>cut bad combination of space point (like TOF_pre)==>CPU power , analysis time

52Cr (77124)

12C (76077)

9Be (76607)10B (76184)7Li (76184) .

×1044

a

b

B.G. mix rate = a/(a+b)

Developing

Generated e+ in Simulation

pe+ : 1.2±0.5 [GeV/c]θ : 0.124±0.124 [rad]φ : 2.64159±0.5 [rad]target : 12C 100[mg/cm2]

HKS D magnetHKS D magnet

Splitter magnet

beam:spherical uniform generation

no collimatorEM flag on