Aerogel Čerenkov Requirements for the SHMS ( e,e’K + ) Program

Aerogel Čerenkov Requirementsfor the SHMS (e,e’K+) Program

Hall C User’s Workshop, August 7, 2009.Hall C User’s Workshop, August 7, 2009.

Garth Huber

2Dr. Garth Huber, Dept. of Physics, Univ. of Regina, Regina, SK S4S0A2, Canada.

SHMS (e,e’K+) Program

So far, three SHMS experiments require good So far, three SHMS experiments require good KK++ identification: identification:

ExperimentExperiment Physics MotivationPhysics Motivation SHMS SHMS Momenta Momenta (GeV/c)(GeV/c)

Worst Worst Fore/Bkd Fore/Bkd Rate RatioRate Ratio

Color Color Transparency Transparency (E12-06-107)(E12-06-107)

• vanishing of vanishing of h-Nh-N interaction at high interaction at high QQ..

• exclusive exclusive ππ, , KK production production from nuclei.from nuclei.

5.1-9.65.1-9.6 1(K):10(p)1(K):10(p)

SIDIS pSIDIS pT T

(E12-09-017)(E12-09-017)

• extract mean kextract mean kTT of u,d,s of u,d,s quarks in proton.quarks in proton.

• SIDIS SIDIS ππ±±, K, K±± production. production.

1.5-5.01.5-5.0

KK FactorizationFactorization(E12-09-011)(E12-09-011)

• study of soft-hard study of soft-hard factorization in exclusive factorization in exclusive KK++ production.production.

• L/T separations vs. L/T separations vs. QQ22, t., t.

2.6-7.12.6-7.1 1(K):3(p)1(K):3(p)


p(e,e’K+) Missing Mass Resolution

Simulation at Simulation at QQ22=2.0 GeV=2.0 GeV22 , , WW=3.0 and high =3.0 and high εε..

• Example from Example from KK++ Factorization Proposal.Factorization Proposal.

• SHMS+HMS missing mass SHMS+HMS missing mass resolution (~30 MeV) resolution (~30 MeV) clearly sufficient to clearly sufficient to separate separate ΛΛ and and Σ°Σ° final final statesstates

• Good Good ππ++/K/K++ ((p/Kp/K++) ) separation using heavy separation using heavy gas (aerogel) Cerenkov is gas (aerogel) Cerenkov is absolutely required.absolutely required.

Λ

Σ°

p(e,e’K+)Λ(Σ°)SHMS+HMS


non-TOF Particle ID @ 1-11 GeV/c

Heavy Gas Čerenkov

Aerogel ČerenkovTOF*

TOF

Dia

gram

from

SH

MS

CD

R

Note: Note: nn=1.02,1.015 leads to poor =1.02,1.015 leads to poor K/pK/p separation at higher momenta. separation at higher momenta.


Aerogel Indices of Refraction (n)

• K/pK/p separation progressively more separation progressively more difficult at higher momenta. difficult at higher momenta.

• To maintain reliable To maintain reliable KK//pp separation separation over a wide momentum range aerogels over a wide momentum range aerogels with variety of with variety of n n are required.are required.

pSHMS

(GeV/c)n(10cm)

K Npe p Npe

2.5-3.0 1.030 13-46 <0.5

3.1-3.7 1.020 12-31 <0.5

3.8-4.3 1.015 13-24 <0.5

4.4-5.1 1.010 5.5- <0.5

5.2-6.2 1.0075 5.5-13 <1

6.4-7.3 1.0055 6-9 <1

Calculation assumes good PMT spectral Calculation assumes good PMT spectral response, 75% light collection efficiency.response, 75% light collection efficiency.


S1 HodoscopeS1 Hodoscope

Space Space Reserved for Reserved for 1-2 Aerogel 1-2 Aerogel ČČerenkovserenkovs

SHMS Detector Stack

Drift ChambersDrift ChambersCC44FF88O O ČČerenkoverenkov

S2 HodoscopeS2 Hodoscope

Ar/Ne Ar/Ne ČČerenkoverenkov

CalorimeterCalorimeter


Aerogel Čerenkov Design Considerations

Requirements:Requirements:• Easy and fast exchange of Aerogel Easy and fast exchange of Aerogel

tray is essential.tray is essential.• Although only one Aerogel Čerenkov Although only one Aerogel Čerenkov

is required at any Pis required at any PSHMSSHMS,,two detectors would reduce two detectors would reduce accesses to swap Aerogel when accesses to swap Aerogel when changing momentum.changing momentum.• Detector must be slenderDetector must be slender..• HMS Aerogel is 25cm thick.HMS Aerogel is 25cm thick.

• Minimum active area: 110x130cmMinimum active area: 110x130cm22..• Compare to 70x120cmCompare to 70x120cm22 for HMS. for HMS.• Division into optically isolated Division into optically isolated

segments could enhance high rate segments could enhance high rate capability.capability. HMS Aerogel Čerenkov

ISO View


HMS Aerogel Čerenkov Performance

• Baseline of 0.6 photoelectrons for sub-threshold particles.Baseline of 0.6 photoelectrons for sub-threshold particles.• ππ detection efficiency in n=1.030 aerogel >99% with detection efficiency in n=1.030 aerogel >99% with NNpepe>4 cut applied.>4 cut applied.• Variation in total light detected varies by up to 20% across focal plane due Variation in total light detected varies by up to 20% across focal plane due

to varying path of light through aerogel to PMT and other factors.to varying path of light through aerogel to PMT and other factors.

R. A

satu

ryan

, et a

l., N

IM A

548

(200

5) 3

64.


Summary• Currently, there are three approved SHMS experiments Currently, there are three approved SHMS experiments

requiring requiring KK++ identification. identification.– Anticipate more experiments with this requirement in future.Anticipate more experiments with this requirement in future.

• Threshold Aerogel Threshold Aerogel Čerenkov Čerenkov detector is simplest and most detector is simplest and most economical way to satisfy economical way to satisfy K/pK/p separation requirement. separation requirement.– ~6 sets of aerogel with different ~6 sets of aerogel with different nn would enable would enable

excellent excellent K/pK/p separation over a wide momentum range. separation over a wide momentum range.– Also helpful to supplement Also helpful to supplement ππ±± identification below 3.4 GeV/c.identification below 3.4 GeV/c.

• Design considerations:Design considerations:– Helpful if aerogel tray can be changed relatively easily.Helpful if aerogel tray can be changed relatively easily.– Very attractive to have 2 Aerogel Čerenkovs in detector Very attractive to have 2 Aerogel Čerenkovs in detector

stack.stack.• Need to watch space requirements very carefully!Need to watch space requirements very carefully!

– SHMS beam envelope more square than HMS.SHMS beam envelope more square than HMS.• Need to avoid efficiency drop in center of detector.Need to avoid efficiency drop in center of detector.

Aerogel Čerenkov Requirements for the SHMS ( e,e’K + ) Program

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