11

SHMS Particle IdentificationSHMS Particle Identification

Hall C User’s Winter Workshop, January 30, 2009.Hall C User’s Winter Workshop, January 30, 2009.

Garth Huber

22Dr. Garth Huber, Dept. of Physics, Univ. of Regina, Regina, SK S4S0A2, Canada.

The limitation of TOFThe limitation of TOF TOF over the short ~2.2m TOF over the short ~2.2m

baseline inside the SHMS baseline inside the SHMS hut will be of little use for hut will be of little use for most of the momentum most of the momentum range anticipated for the range anticipated for the SHMS.SHMS.

Even over a 22.5m Even over a 22.5m distance from the target to distance from the target to the SHMS detector stack, the SHMS detector stack, TOF is of limited use.TOF is of limited use.

Effect of finite timing resolution Effect of finite timing resolution (±1.5(±1.5σσ with with σσ=200ps).=200ps).Separation <3Separation <3σσ to the right of to the right of where lines intersect.where lines intersect.

33Dr. Garth Huber, Dept. of Physics, Univ. of Regina, Regina, SK S4S0A2, Canada.

Non-TOF techniquesNon-TOF techniques Efficient, high-confidence PID requires Efficient, high-confidence PID requires

extensive use of non-TOF techniques such as extensive use of non-TOF techniques such as Čerenkov detectors.Čerenkov detectors.

Good PID can be obtained with a series of Good PID can be obtained with a series of Čerenkov detectors:Čerenkov detectors: ee-/-/ππ-- Noble Gas Čerenkov Noble Gas Čerenkov (n-1 < 10(n-1 < 10-4-4)) ππ++//KK++ Heavy Gas Čerenkov Heavy Gas Čerenkov (n-1 ≤ 10(n-1 ≤ 10-3-3)) KK++/p/p Aerogel Čerenkov Aerogel Čerenkov (n-1 ≤ 0.05)(n-1 ≤ 0.05)

Lead Glass Calorimeter also plays a critical role Lead Glass Calorimeter also plays a critical role in ein e--,e,e++ identification. identification.

44Dr. Garth Huber, Dept. of Physics, Univ. of Regina, Regina, SK S4S0A2, Canada.

Noble Gas ČerenkovNoble Gas Čerenkov:: e/π separation at high momenta, where multiple-scattering is less of an issue.

Trigger HodoscopesTrigger Hodoscopes:: Time-of-Flight at low momenta; insensitive to photon or low-energy background.

Heavy Gas ČerenkovHeavy Gas Čerenkov:: π/K separation for P>3.4 GeV/c.

Aerogel Čerenkov(s):Aerogel Čerenkov(s):Depending on the n used, K/p separation orπ/K separation at low momenta.

Lead Glass CalorimeterLead Glass Calorimeter: : e/π separation.

Hall-C SHMS Detector SystemHall-C SHMS Detector System

55Dr. Garth Huber, Dept. of Physics, Univ. of Regina, Regina, SK S4S0A2, Canada.

Calorimeter: e/Calorimeter: e/π π separationseparation

Side Side ElevationElevation

Front ElevationFront Elevation

Plan viewPlan view •Lead-Glass Block / PMT / Base Assemblies from HERMES.•Expect >200:1, based on HMS Calorimeter performance.

66Dr. Garth Huber, Dept. of Physics, Univ. of Regina, Regina, SK S4S0A2, Canada.

Noble Gas Cerenkov: e/Noble Gas Cerenkov: e/ππ (or (or ππ /K) /K) separation at high momentaseparation at high momenta

2.5 m long gas radiator at atmospheric pressure.•Argon: π threshold ~ 6 GeV/c.•Adding Neon: π threshold may be varied up to 12 GeV/c.•Para-Terphynyl PMT window over-coating .•Performance 20 photoelectrons

(worst case: pure Neon).

At low momenta: remove mirrors, insert coupling so that the tankbecomes part of the vacuum system – reduces MCS.

77Dr. Garth Huber, Dept. of Physics, Univ. of Regina, Regina, SK S4S0A2, Canada.

Heavy Gas Cerenkov: Heavy Gas Cerenkov: ππ/K separation for /K separation for momenta > 3.4 GeV/cmomenta > 3.4 GeV/c

To maintain good To maintain good ππ//K K separation, it is necessary separation, it is necessary to reduce the gas pressure to reduce the gas pressure above 7 GeV/c.above 7 GeV/c.

Lowest π± identification efficiency occurs at 3.4 GeV/c (~10 p.e.).

88Dr. Garth Huber, Dept. of Physics, Univ. of Regina, Regina, SK S4S0A2, Canada.

Electron-Pion DiscriminationElectron-Pion Discrimination

The most stringent requirements arise when the The most stringent requirements arise when the SHMS is set to negative polarity.SHMS is set to negative polarity.

Both eBoth e--//ππ-- and and ππ--/e/e-- separations are required: separations are required:

ExptExpt PPSHMSSHMS

(GeV/c)(GeV/c)Worst Fore/Bkd Worst Fore/Bkd Rate RatioRate Ratio

Noble Gas ČNoble Gas Č Pb-G Pb-G CalCal

Total e:Total e:ππ RejectReject

FFππ (E12-06-101) (E12-06-101) 5.1,6.55.1,6.5 1 (1 (ππ-):1000(e-)-):1000(e-) 50:150:1 200:1200:1 10000:110000:1

SIDIS pSIDIS pTT

(PR12-09-017)(PR12-09-017)

1.5-5.01.5-5.0 1 (1 (ππ-):10 (e-)-):10 (e-) Not used for Not used for lowest P.lowest P.

250:1250:1 250:1250:1

x>1 (E12-06-105)x>1 (E12-06-105) 4.8-10.64.8-10.6 1(e-):50(1(e-):50(ππ-)-) 50:150:1 100:1100:1 5000:15000:1

DIS-parity DIS-parity

(E12-07-102)(E12-07-102)

4.9-6.74.9-6.7 3(e-):1(3(e-):1(ππ-)-) 10:110:1 100:1100:1 1000:11000:1

99Dr. Garth Huber, Dept. of Physics, Univ. of Regina, Regina, SK S4S0A2, Canada.

Pion-Kaon DiscriminationPion-Kaon Discrimination

Equally applicable for positive or negative SHMS Equally applicable for positive or negative SHMS polarity.polarity.

Supplemental Aerogel or TOF must supplement Supplemental Aerogel or TOF must supplement Heavy Gas Čerenkov at low momentum.Heavy Gas Čerenkov at low momentum.

ExptExpt PPSHMSSHMS

(GeV/c)(GeV/c)Worst Worst Fore/Bkd Rate Fore/Bkd Rate RatioRatio

Heavy Gas ČHeavy Gas Č

P>3.4 GeV/cP>3.4 GeV/c

Aerogel ČAerogel Č

P<3.4 GeV/cP<3.4 GeV/c

(n=1.010)(n=1.010)

FFππ (E12-06-101) (E12-06-101) 2.2-8.12.2-8.1 2(2(ππ):3(K+p)):3(K+p) 1000:11000:1 300:1300:1

CT (E12-06-107)CT (E12-06-107) 5.1-9.65.1-9.6 1(1(ππ):1(K+p)):1(K+p) 1000:11000:1 NANA

ππ Factorization Factorization

(E12-07-102)(E12-07-102)

2.4-8.52.4-8.5 2(2(ππ):3(K+p)):3(K+p) 1000:11000:1 300:1300:1

K FactorizationK Factorization

(PR-09-011)(PR-09-011)

2.6-7.12.6-7.1 1(K):30(1(K):30(ππ)) 1000:11000:1

1010Dr. Garth Huber, Dept. of Physics, Univ. of Regina, Regina, SK S4S0A2, Canada.

Aerogel ČerenkovAerogel Čerenkov Reliable Reliable KK//pp separation over a wide momentum range is a challenge. separation over a wide momentum range is a challenge. Although only one aerogel Čerenkov is required at any particular Although only one aerogel Čerenkov is required at any particular

momentum, two detectors would allow flexibility over a greater range.momentum, two detectors would allow flexibility over a greater range. K/pK/p separation gets progressively more difficult as (n-1) is reduced at separation gets progressively more difficult as (n-1) is reduced at

higher momenta.higher momenta.

ppSHMS SHMS

(GeV/c)(GeV/c)nn

(10cm)(10cm)

K p.e.K p.e. p p.e.p p.e.

2.5-3.02.5-3.0 1.0301.030 13-4613-46 <0.5<0.5

3.1-3.73.1-3.7 1.0201.020 12-3112-31 <0.5<0.5

3.8-4.33.8-4.3 1.0151.015 13-2413-24 <0.5<0.5

4.4-5.14.4-5.1 1.0101.010 5.5-5.5- <0.5<0.5

5.2-6.25.2-6.2 1.00751.0075 5.5-135.5-13 <1<1

6.4-7.36.4-7.3 1.00551.0055 6-96-9 <1<1

1111Dr. Garth Huber, Dept. of Physics, Univ. of Regina, Regina, SK S4S0A2, Canada.

Kaon-Proton DiscriminationKaon-Proton Discrimination

Only relevant for SHMS positive polarity.Only relevant for SHMS positive polarity. Several experiments have similar stringent Several experiments have similar stringent

requirements:requirements:

ExptExpt Momenta Momenta (GeV/c)(GeV/c)

Worst Fore/Bkd Worst Fore/Bkd Rate RatioRate Ratio

Aerogel ČAerogel Č

(worst case)(worst case)

CT (E12-06-107)CT (E12-06-107) 5.1-9.65.1-9.6 1(K):10(p)1(K):10(p) 100:1100:1

SIDIS pSIDIS pT T

(PR12-09-017)(PR12-09-017)

1.5-5.01.5-5.0 200:1200:1

K FactorizationK Factorization

(PR12-09-011)(PR12-09-011)

2.6-7.12.6-7.1 1(K):3(p)1(K):3(p) 100:1100:1

Additional PID helpful at higher P

1212Dr. Garth Huber, Dept. of Physics, Univ. of Regina, Regina, SK S4S0A2, Canada.

Supplementary K/Supplementary K/ππ 7 GeV/c 7 GeV/c pCDR includes a supplemental K/π identification technique

utilizing the dE/dx distribution of particles traversing the wire chambers.

Requires analog readout for groups of wires.

7 GeV/c π:K

Cut placed at75% likelihoodresults in200:1 π:K sep.separation with95% efficiency.

LikelihoodLikelihood

1313Dr. Garth Huber, Dept. of Physics, Univ. of Regina, Regina, SK S4S0A2, Canada.

SummarySummary Particle identification requirements of approved and Particle identification requirements of approved and

proposed SHMS experiments are largely met by the proposed SHMS experiments are largely met by the planned detector package.planned detector package.

At least one Aerogel Čerenkov is required for At least one Aerogel Čerenkov is required for ππ±± identification at P<3.4 GeV/c and for Kidentification at P<3.4 GeV/c and for K±± identification identification up to at least 5 GeV/c.up to at least 5 GeV/c.

The need to supplement K identification at higher The need to supplement K identification at higher momenta seems clear.momenta seems clear. Addition of pulse-height info to the wire chamber Addition of pulse-height info to the wire chamber

readout is a particularly attractive option.readout is a particularly attractive option. Requires new readout electronics, but cost is Requires new readout electronics, but cost is

offset by the need for fewer sets of aerogel offset by the need for fewer sets of aerogel (different n) and less overhead when changing (different n) and less overhead when changing momentum.momentum.

Likely cost effective over the longer term.Likely cost effective over the longer term.