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ハイパー核ガンマ線分光用 磁気スペクトロメータ -SksMinus-. 東北大学 大学院理学研究科 白鳥昂太郎 12/14 @ ATAMI. Outline. Background of experiments Requirement on setup Modification of SKS Setup : SksMinus Detectors in detail, DC, Veto counters Summary Future plan. “DAY-1” experiment E13.

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Sksminus

ハイパー核ガンマ線分光用磁気スペクトロメータ-SksMinus-

東北大学 大学院理学研究科

白鳥昂太郎

12/14 @ ATAMI


Outline
Outline

  • Background of experiments

  • Requirement on setup

  • Modification of SKS

  • Setup : SksMinus

  • Detectors in detail, DC, Veto counters

  • Summary

  • Future plan

2006 Strangeness ATAMI


Day 1 experiment e13
“DAY-1” experimentE13

  • Several light hypernuclear gamma-ray spectroscopy experiments are planned.

    (4LHe, 7LLi, 10LB, 11LB, 19LF)

Beam momentum

  • (K-, p-g) @ 1.5 GeV/c (500 k/spill, full intensity)

  • The best sensitivity for selecting spin-flip state

  • 1.1~1.8 GeV/c beam for 4LHe

K- + n-> L + p-

2006 Strangeness ATAMI


Requirement on spectrometer for hypernuclear gamma ray spectroscopy
Requirement on spectrometer forhypernuclear gamma-ray spectroscopy

  • To analyze 1.4 GeV/c (1.1~1.8 GeV/c) scattered p- byexistingspectrometer system

  • Large acceptance ~100 msr, q~20 degree

    → Enough hypernuclear production yield.

  • Good momentum resolution 2~4 MeV/c

    → To distinguish excited states of hypernuclei

SksMinus

(Superconducting Kaon Spectrometer

Modified for Hypernuclear Gamma ray Spectroscopy)

2006 Strangeness ATAMI



The modification of sks
The modification of SKS

Present SKS

2.2T

2.7T

q~20°

q~20°

1.05 GeV/c (p+, K+) reaction (K+ 0.72 GeV/c)

  • Scattered particles are not focused and present drift chambers (SDC3,4)are small for large reaction angle (half acceptance).

2006 Strangeness ATAMI


The modification of sks1
The modification of SKS

  • Keeping large acceptance and wide angular coverage by large drift chambers (2m×1m) (from BNL and Freiburg)

  • Incident beam angle and position of drift chambers are optimized by keeping acceptance for the 1.5 GeV/c beam condition.

  • Setup can be used for 1.1~1.8 GeV/c beam hypernuclear gamma ray spectroscopy experiment without modification.

q~20°

2006 Strangeness ATAMI


The modification of sks2
The modification of SKS

  • Keeping large acceptance and wide angular coverage by large drift chambers (2m×1m) (from BNL and Freiburg)

  • Incident beam angle and position of drift chambers are optimized by keeping acceptance for the 1.5 GeV/c beam condition.

  • Setup can be used for 1.1~1.8 GeV/c beam hypernuclear gamma ray spectroscopy experiment without modification.

On the step, not a giant

270cm

170cm

2006 Strangeness ATAMI


The k1 8 beam line and sksminus
The K1.8 Beam line and SksMinus

Beam spectrometer

・BH1,2 : Time-of -flight

・BAC : p- veto (n=1.03)

SksMinus

・STOF : Time-of-flight

・SAC : K- beam veto (n=1.03)

・SFV : K- beam veto

Target : ~20 g/cm2

Length : 20 cm

MWPC & DC

: Beam position measurement

Background Veto

・SMF : m- from K- → m- + n

・SP0 : p- from K- → p- + p0

Hyperball-J : g ray

T.Koike 12/15

2006 Strangeness ATAMI


Sksminus1
SksMinus

SksMinus

・SAC : K- beam veto (n=1.03)

・SFV : K- beam veto

・STOF : Time-of-flight

SDC1~4

: Beam position measurement

Background Veto

・SMF : m- from K- → m- + n

・SP0 : p- from K- → p- + p0

Target : ~20 g/cm2

Length : 20 cm

2006 Strangeness ATAMI


Sksminus performance basic performance

SksMinus performanceBasic performance

Acceptance

Momentum resolution


Acceptance
Acceptance

  • Acceptance at 1.4 GeV/c ~130 msr by large drift chambers (2m×1m)

  • Angular acceptance is enough, ~ 20 degree

  • Acceptance is determined by SKS magnet gap and distance from SKS entrance.

  • Higher momentum

    → Cut off by SKS magnet

  • Lower momentum

    → Out of range SDC3,4

2006 Strangeness ATAMI


Momentum resolution
Momentum resolution

  • Momentum resolution at 1.4 GeV/c ~2.1 MeV/c (FWHM) ,intrinsic ~1.6, MSC ~1.3

  • 400 mm DC resolution and multiple scattering (DC : Ar gas, He bag : He gas, Air)

  • Higher momentum

    → Intrinsic resolution (bending angle)

  • Lowe momentum

    → Similar to present SKS,

    ~0.9 MeV/c (FWHM) @ 1.0 GeV/c

2006 Strangeness ATAMI


Sksminus performance beam decay suppression

SksMinus performanceBeam decay suppression

Muon Filter

PiZero Veto


Background rejection

Target

20cm

BAC

SAC

p

Beam K

Reaction

Background rejection

Beam K- decay products make serious background (Trigger rate, Missing mass spectrum)

  • K- → m-n (63.4%)

    ⇒Muon Filter(1390 /spill)

  • K- → p- p0 (21.1%)

    ⇒PiZero Veto (350 /spill)

Fake trigger ~1740/spill

True event trigger ~1000/spill

(Contribution of three-body decay ~200 /spill)

2006 Strangeness ATAMI


Background rejection1

Target

20cm

BAC

SAC

m

Beam K

Decay

n

Background rejection

Beam K- decay products make serious background (Trigger rate, Missing mass spectrum)

  • K- → m- n (63.4%)

    ⇒Muon Filter(1390 /spill)

  • K- → p- p0 (21.1%)

    ⇒PiZero Veto (350 /spill)

Fake trigger ~1740/spill

True event trigger ~1000/spill

(Contribution of three-body decay ~200 /spill)

2006 Strangeness ATAMI


Muon filter smf
Muon Filter -SMF-

Stopping points

p- (stopped in the iron)

m momentum

m- (passing through)

  • 86% of m can be rejectedin the trigger @ 1.5 GeV/c beam

  • Stopped m cannot be rejected.

    (In the offline analysis >99%)

  • Over kill for true π ~2.5%

Not need to change iron thickness, 1.1~1.8 GeV/c beam

2006 Strangeness ATAMI


Muon filter smf1
Muon Filter -SMF-

Stopping points

X

m-

Z

p-

m momentum

  • 86% of m can be rejectedin the trigger @ 1.5 GeV/c beam

  • Stopped m cannot be rejected.

    (In the offline analysis >99%)

  • Over kill for true π ~2.5%

Not need to change iron thickness, 1.1~1.8 GeV/c beam

2006 Strangeness ATAMI


Pizero veto sp0
PiZero veto -SP0-

Acceptance 85%

  • 78% of p0 can be detected by 6 sets of 5 mm lead plate and scintillation counter layer at 1.5 GeV/c beam.

    (85% of g from p0 hit the SP0)

Reaction p- pass through the window.

2006 Strangeness ATAMI


Pizero veto sp01
PiZero veto -SP0-

Acceptance 85%

  • 78% of p0 can be detected by 6 sets of 5 mm lead plate and scintillation counter layer at 1.5 GeV/c beam.

    (85% of g from p0 hit the SP0)

Reaction p- pass through the window.

2006 Strangeness ATAMI


Trigger rate @ 1 5 gev c beam
Trigger rate @ 1.5 GeV/c beam

(K-, p- g) at pK = 1.5 GeV/c (500 k/spill)

  • (K-,π-) Reaction rate ~1000 /spill

  • K-→m- n ~1390 /spill

  • K-→p- p0 ~350 /spill

  • K- Beam ~30 /spill

  • 3-body decay ~200 /spill

~2970 /spill

w/o Veto counters

True trigger ~500 /spill

w/ Ge trigger and fake trigger greatly decreased (1/4).

  • (K-,π-) Reaction rate ~950 /spill

  • K-→m- n~190 /spill

  • K-→p- p0~80 /spill

  • K- Beam ~30 /spill

  • 3-body decay ~70 /spill

~1320/spill

w/ Veto counters

~570/spill

w/ Ge trigger

Comparable to the present trigger rate

2006 Strangeness ATAMI


4 l he experiment
4LHe experiment

  • Energy spacing of 4LHe(1+) → 4LHe(0+), (4LH(1+) → 4LH(0+) : (K-, p0 ), no charge and SP0 ?)

    @ 1.5 GeV/c beam M.Ukai 12/15

  • Spin-flip measurement

  • Momentum (1.1), 1.3, 1.5, 1.8 GeV/c

  • →Acceptance and momentum resolution are enough.

  • PID counters

  • →STOF, SAC and SFV are enough.

  • Veto counters

  • →More study is needed : Trigger rate @ 1.8 GeV/c.

K- + n-> L + p-

2006 Strangeness ATAMI


Summary
Summary

  • Several hypernulcear gamma-ray experiments are planned at the J-PARC K1.8 beam line (4LHe, 7LLi, 10LB, 11LB, 19LF).

  • SksMinus is sufficient for hypernuclear gamma-ray spectroscopy at 1.5 GeV/c beam. Acceptance 130 msr, 20 degree. Momentum resolution 2.1 MeV/c.

  • Simulations in progress show a good veto counter efficiency at 1.5 GeV/c beam, SMF ~86%, SP0 ~78%.

  • SksMinus can be used for 1.1~1.8 GeV/c beam.

2006 Strangeness ATAMI


Future plan
Future Plan

  • Determination of the final SksMinus design

  • SDC3&4 shipped from BNL and Freiburg and repaired in 2007

  • PMT for TOF and Cherenkov from BNL D6 beam line and Range counter (E559) in 2007

  • Design and construction of SMF, SP0 and other counters in 2007~2008

2006 Strangeness ATAMI



Particle identification
Particle identification

  • (K-, p- ) → p- or K-

  • Beam K- can greatly be decreased by SAC (n=1.03) and SFV

  • → less than 30 trigger /spill (500 k/spill beam)

  • Time resolution of STOF ~150 ps (rms)

  • For B(M1) measurement, dual SAC is planned because of saving forward events.

2006 Strangeness ATAMI


Magnetic field
Magnetic field

Calculated magnetic filed map is used in simulations.

2006 Strangeness ATAMI


The modification of sks3
The modification of SKS

  • Large acceptance and wide angular coverage by large drift chambers (2m×1m)

  • Incident beam angle and position of drift chambers are optimized by keeping acceptance for the 1.5 GeV/c beam condition.

  • Setup can be used for 1.1~1.8 GeV/c beam hypernuclear gamma ray spectroscopy experiment without modification.

2006 Strangeness ATAMI


Beam veto
Beam Veto

  • SAC efficiency ~99%

    →5k trigger /spill @ 500k/spill

    SFV →~10 trigger

    Reduction of acceptance 7.5%

  • Beam size

    σx=19.8 mm

    σy=3.2 mm

    (u=0.02, v=0.002)

  • SBS

    K- beam directly hit SDC3,4.

    Scattering beam particles by some material (Pb, W)

    300kHz → [email protected] 20mm cell

SBS

2006 Strangeness ATAMI


Smf sp0 performance @ 1 1 1 8 gev c beam
SMF & SP0 performance @ 1.1~1.8 GeV/c beam

SMF

SP0

m- ~580 trigger/spill

@ 1.8 GeV/c beam

(~4300 trigger)

p- ~360 trigger/spill

@ 1.8 GeV/c beam

(~1200 trigger)

It is difficult to suppress trigger rate at higher beam intensity…

2006 Strangeness ATAMI


3 body decay
3-body Decay

K-→π-π-π+ (5.58%)

K-→e-π0ν (4.87%)

K-→μ-π0ν (3.27%)

K-→π-π0π0 (1.73%)

2006 Strangeness ATAMI


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