Transversity at CLAS

1
The focusing mirror system

• spherical (elliptical) mirror within gap volume
  for backward refl.
• plane mirror just beyond radiator for forward
  reflections

Preliminary studies with mirrors (to reduce
instrumented area) - focalization
capabilities shown - ring patterns for positive
and negative mesons at different angles and
momenta reconstructed
Different scenarios (refractive index, radiator
thickness, mirror geometry) are being explored
2
Hit prob gt 3 10-4
Hit prob
3
Unidentified events reduced by better
treatment of unwanted events (i.e. muon
from meson decay) Mismatch in number of N
p.e. wrong seed assignment Protons
weird probability feature of the LH
definition close to the threshold
4
Direct ring example
Hit prob gt 3 10-3
200 trials per point
Aerogel - n1.06 - thick. increasing
with radius 2-4-6-8-10 cm Mirror
14-25o PMTs UBA
Hit prob
5
Hybrid ring example
Hit prob gt 3 10-3
200 trials per point
Aerogel - n1.06 - thick. increasing
with radius 2-4-6-8-10 cm Mirror
14-25o PMTs UBA
Hit prob
6
Average N p.e. Mirror 14-25o PMTs UBA
200 trials per point
Aerogel - n1.06 - thick. increasing
with radius 2-4-6-8-10 cm
N p.e. gt 5 for reflected rings N p.e. gt 12 for
direct rings
7
LHp-LHk,p Mirror 14-25o PMTs UBA
200 trials per point
Aerogel - n1.06 - thick. increasing
with radius 2-4-6-8-10 cm
Low angles more challenging Possibly due to
limited number of trials
Protons benefit the small number of unfired PMTs
whit expected signal (P is small when C0)
-
8
Average N p.e. Mirror 14-25o PMTs UBA
200 trials per point
Aerogel - n1.06 - thick. increasing
with radius 2-4-6-8-10 cm
Mandatory for positive hadrons Benefit for
negative hadrons at large angles and small energy
Big dot studies show in the previous slide
9
Average N p.e. PMTs UBA
Mirror 14-25o
Mirror 14-35o
Worse for positive hadrons Better for negative
hadrons
10
LHp-LHk,p PMTs UBA
Mirror 14-25o
Mirror 14-35o
Worse for positive hadrons Better for negative
hadrons
11
Average N p.e. PMTs UBA
200 trials per point
Aerogel - n1.06 - thick. increasing
with radius 2-4-6-8-10 cm
Mirror up to 35o Worse for positive
hadrons Better for negative hadrons
12
Average N p.e. Mirror 14-25o PMTs UBA
n1.03 Aer. thick 3-6-9-12-15 cm
n1.06 Aer. thick 2-4-6-8-10 cm
n1.03 gives less photons regardeless the
increase thickness due to same assumed
transmission length
13
LHp-LHk,p Mirror 14-25o PMTs UBA
n1.03 Aer. thick 3-6-9-12-15 cm
n1.06 Aer. thick 2-4-6-8-10 cm
n1.03 still good due to the larger Cherenkov
angle separation
14
Average N p.e. PMTs UBA
200 trials per point
Aerogel - n1.06 - thick. increasing
with radius 2-4-6-8-10 cm
n1.06 better for patter recognition in the
presence of backgrouns
15
Wrong ID example
Hit prob gt 3 10-3
200 trials per point
Aerogel - n1.06 - thick. increasing
with radius 2-4-6-8-10 cm Mirror
14-25o PMTs UBA
Hit prob