Status of Compton Analysis

Yelena ProkPrimEx Collaboration MeetingJune 23, 2006

Outline

Recent changes Pair-contamination Most recent yields What needs to be done

(Trigger) Bit 9! Bit 2

Multiplicity of bit 9 Multiplicity of bit 2

makes more sense

(Trigger) Bit 9! Bit 2

Bit 9Bit 2

Hycaltime(bit9)-TAGM.t Hycaltime(bit2)-TAGM.t

No major changes in time distribution

Event Selection Run 5150 To select a photon:

choose the one closest in time to HYCAL (10 ns window)

To select a pair of clusters: choose the one with (E1+E2) closest to Ecompton where

Ecompton=[me*sin]/[2*sin2(/2)*tanel]-me

Effect of geometric cuts

100K,No cuts

25.3K, emin cut

13.3K, emin, hole, vert cut 19.5K emin+hole cut

Acceptance by TCountergeometry

TCounter tchannes Emin/GeV Emax/GeV Accept(%)

1 1+2 5.45 5.5 12.1199

2 3+4 5.39 5.45 12.3939

3 5+6 5.32 5.39 12.5794

4 7+8 5.27 5.32 12.6812

5 9+10 5.22 5.27 12.8210

6 11+12 5.17 5.22 13.0388

7 13+14 5.12 5.17 13.1560

8 15+16 5.07 5.12 13.3083

9 17+18 5.01 5.07 13.4043

10 19+20 4.95 5.01 13.4107

11 21 4.89 4.95 13.5542

Counting Events

GeV cm

Ebeam- EcompZ

N N

Be target, TCounter 2

N N

Geom cut, +elasticity cut (20 %)

Normalized Yield per electron Acceptance corrected normalized

yield NCNY: NCNY=N/L/A N=counts under the first gaussian

function L=*th*NA* th=target thickness =target density NA=Avogadro’s Number =atomic mass A=geometric acceptance obtained

from simulation

Detection efficiency and reconstruction efficiency are not known and set to 1

Yield vs Run

Consistent except for run 4972

TCounter 1 TCounter 2

Compare 2 regions

1 2

Region 1 vs Region 2

both charged

one charged

mix

ptx

pty

GeVGeV

Region 1 vs Region 2 (cont)

Z

cm cm

separation

Region 1 vs Region 2 (cont)

GeV GeV

deg deg

mostly pairs what are these?

Summary Current yields are

on average ~10% below expectation

Need to understand the background, efficiency and effect of cuts on the data !

Need full MC (trying to make sense out of “primsim”,

not very successfully so far)J’ai besoin d’aide…

Compton event in “primsim”