スライド 1

SksMinus
status
19
HB meeting
2009/2/06
白鳥昂太郎
Contents
 Trigger rate study

In particular, S trigger (子熊とりがー)
Trigger candidate of E13 experiment

(K-, p-) reaction : True trigger (積極的に検出)
 Hypernuclear production : AZ(K-, p-)ALZ
 Quasi-free : n(K-, p-)L, n(K-, p-)S0, p(K-, p-)S+
pK=1.5 GeV/cでは、これらすべての反応がSksMinusのacceptanceに入る

その他色々 : N(K-, p-)Y+p, N(K-, p-)Y+N+p, A(K-, p-)A*+Y...
pK=1.5 GeV/cでは、ほぼSksMinusのacceptance外か

K- beam decay (vetoed by SMF, SP0)
 2-body: K-→m-+nmbar, p-+p0
 3-body: K-→ p-+p0+p0, p-+p++p-, m-+nmbar+p0, e-+nebar+p0

Bema through (vetoed by BAC, SAC)
 K- →K p- →p pbar, e-, m-とか
Expected trigger number : 10 cm 7Li target (20 cm effective region)

(K-, p-) reaction : True trigger
W/o S
n(K-, p-)L : ~600 /spill (quasi-free main)

n(K-, p-)S0, p(K-, p-)S+ : ??

N(K-, p-)Y+p, N(K-, p-)Y+N+p... : Smaller cross section and almost out of SksMinus acceptance
⇒ 600+S trigger


K- beam decay vetoed by SMF, SP0
2-body: K-→m-+nmbar : 1400 ⇒ ~200 /spill

K-→ p-+p0 : 400 ⇒ ~100 /spill

3-body: K-→ p-+p0+p0, p-+p++p-, m-+nmbar+p0, e-+nebar+p0 : 80 ⇒~10 /spill
⇒ W/o veto : 1400+400+80=2880 /spill
⇒ W/ veto : 200+100+10=310 /spill


Bema through vetoed by BAC, SAC



K- →K- : 500 k/spill×0.01×0.01= 50 /spill
p- →p- : 200 k/spill×0.01×0.01= 20 /spill
pbar, e-, m-とか: とりあえず無視 (m-はp- と似たような数勘定になるが)
Total
w/o Ge hit : (600) + (200 + 100 + 10) + (50 + 20) + S trigger = 980 /spill + S trigger
(w/o Ge hit : (600) + (1400 + 400 + 80) + (50 + 20) + S trigger = 2550 /spill + S trigger)
w/ Ge hit : Total/2 = ~500 /spill + S trigger/2
w/ Ge hit : Reaction/2 + decay/3 + no-beam = ~400 /spill + S trigger/2
How much S trigger ? Ge trigger is essential !
Reaction trigger for Ge hit
Elementally process (quasi-free reaction)

n(K-, p-)L : Lp+p- (64%), n+p0 (36%)

n(K-, p-)S0 : S0L+ (100%)L p+p- (64%), n+p0 (36%)

p(K-, p-)S+ : S+ p+p0 (52%), n+p+ (48%)
p-やp0→2, がGeにhit
⇒おおよそ生成量とHyperball-J acceptanceで量が決まる
1.

HBJ acceptance ~30%程度 (target内部等方生成),
(p0→2は必ずGeにhit, p-はacceptanceをhitとした)
Lの場合 : 0.3*0.64 + 0.36 = 0.55
Sの場合 : 0.3*0.48 + 0.52 = 0.66
⇒Reaction trigger/2はおおよそ妥当 (か?⇒E930 dataの再現)
pやnで周辺物質に励起状態の原子核ができ、 を出す
3.
Quasi-free反応で標的の原子核に励起状態ができ、それがや核子を出す
⇒これらのプロセスでもGe hitは増加する
(1はsimulation可能。2,3は難しい…)
2.
L生成cross section
@ 1.5 GeV/c
Quasi-freeだと変わるが、とりあえずこれで計算 : 0.3 mbくらい (q<15°)
⇒~600 /spill (500 k/spill beam, 20 cm 7Li target)
(SksMinusのacceptanceを考慮)
S生成cross section
p(K-, p-)S+ deferential
n(K-, p-)S0 total
L, S生成cross section
Total cross section
 n(K-, p-)L : ~2.2 mb (exp.)
 n(K-, p-)S0 : ~0.5 mb (exp.)
 p(K-, p-)S+ : ~1.2 mb (exp.)
Deferential cross section
 n(K-, p-)L : ~0.3 mb (exp.) @ pK=1.5 GeV/c, q<15°
 p(K-, p-)S+ : ~0.2 mb (exp.) @ pK=1.43 GeV/c, q<18°
( cos(q) > 0.95での平均とした)
⇒S生成trigger数はL生成と同程度として多めに見積もって
みる
Expected trigger number : 10 cm 7Li target (20 cm effective region)

(K-, p-) reaction : True trigger
n(K-, p-)L : ~600 /spill (quasi-free main)

n(K-, p-)S0, p(K-, p-)S+ : ~600 /spill (quasi-free main)

N(K-, p-)Y+p, N(K-, p-)Y+N+p... : Smaller cross section and almost out of SksMinus acceptance
⇒ 600+600 = 1200 /spill


K- beam decay vetoed by SMF, SP0
2-body: K-→m-+nmbar : 1400 ⇒ ~200 /spill

K-→ p-+p0 : 400 ⇒ ~100 /spill

3-body: K-→ p-+p0+p0, p-+p++p-, m-+nmbar+p0, e-+nebar+p0 : 80 ⇒~10 /spill
⇒ W/o veto : 1400+400+80=2880 /spill
⇒ W/ veto : 200+100+10=310 /spill


Bema through vetoed by BAC, SAC



K- →K- : 500 k/spill×0.01×0.01= 50 /spill
p- →p- : 200 k/spill×0.01×0.01= 20 /spill
pbar, e-, m-とか: とりあえず無視 (m-はp- と似たような数勘定になるが)
Total
w/o Ge hit : (600 + 600) + (200 + 100 + 10) + (50 + 20) = 1580 /spill
(w/o Ge hit : (600 + 600) + (1400 + 400 + 80) + (50 + 20) = 3150 /spill)
w/ Ge hit : Total/2 = ~800 /spill
w/ Ge hit : Reaction/2 + decay/3 + no-beam = ~700 /spill
Ge hitの見積もりに依るが、Trigger rateは現DAQではギリギリ ⇒ Ge triggerをGe×PWOか？
各targetでのtrigger
4 He
L
反応を羅列
 True : 4He(K-, p-)4LHe ⇒ 4LHeのdecay
 -decay : 4LHe*→4LHe+
 Weak decay : 4LHe→4He+p0, 3He+n+p0, 3He+p+p Quasi-free production
 4He(K-, p-)3He+L : L decay
 4He(K-, p-)3He+S0 : S0 decay
 4He(K-, p-)3H+S+ : S+ decay
 3H*, 3He*, 4He(K-, p-) 3N+Y, 2N+N+Y, N+N+N+Yは無視
特殊な条件
 物質量が小さい : n(K-, p-)L : ~80 /spill
 Targetが長い
⇒Mainにはbeam decayが効く
Expected trigger number : 25 cm 4He target (40 cm effective region)

(K-, p-) reaction : True trigger
n(K-, p-)L : ~80 /spill (quasi-free main)

n(K-, p-)S0, p(K-, p-)S+ : ~80 /spill (quasi-free main)

N(K-, p-)Y+p, N(K-, p-)Y+N+p... : Smaller cross section and almost out of SksMinus acceptance
⇒ 80+80 = 160 /spill


K- beam decay vetoed by SMF, SP0
2-body: K-→m-+nmbar : 2800 ⇒ ~400 /spill

K-→ p-+p0 : 800 ⇒ ~200 /spill

3-body: K-→ p-+p0+p0, p-+p++p-, m-+nmbar+p0, e-+nebar+p0 : 160 ⇒~20 /spill
⇒ W/o veto : 2800+800+160=3760 /spill
⇒ W/ veto : 400+200+20=620 /spill


Bema through vetoed by BAC, SAC



K- →K- : 500 k/spill×0.01×0.01= 50 /spill
p- →p- : 200 k/spill×0.01×0.01= 20 /spill
pbar, e-, m-とか: とりあえず無視 (m-はp- と似たような数勘定になるが)
Total
w/o Ge hit : (80 + 80) + (400 + 200 + 20) + (50 + 20) = 850 /spill
(w/o Ge hit : (80 + 80) + (1400 + 400 + 80) + (50 + 20) = ~4000 /spill)
w/ Ge hit : Total/2 = ~450 /spill
w/ Ge hit : Reaction/2 + decay/3 + no-beam = ~300 /spill
Decay vetoで大幅にtrigger rateを減らせる
7 Li, 10 B, 11 B, 19 F
L
L
L
L


(+
12 C, 16 O)
L
L
どれも10 cmのtarget長なのでreaction triggerがmain
になる
標的の核子数が多く、励起状態からの粒子放出が増え
るので、Geが鳴る割合が増える


放出 ⇒ によるGe trigger
核子放出 ⇒ 周辺物質からのbackground 
Ge triggerにも依るが、ｔrigger rateは現DAQではギリ
ギリ
⇒ Ge triggerをGe×PWOでどの程度まで改善できるか?

Summary

S reaction triggerはLと同程度
 4LHe実験はdecay
eventでtrigger数が決まる
⇒単純な(K, p) triggerとGe triggerでも問題なし
 7LLi, 10LB, 11LB, 19LF (+ 12LC, 16LO)実験ではGe triggerを
工夫しないと若干厳しい


1k /spill程度のtrigger rateならば、安直に早いADC,
TDCモジュールの導入が理想的
将来的に10 M/spillのintensityが出たときにどうするか？

800 /spill (@500 k/spill)⇒16000 /spill !
E930 trigger condition

KPi = Kin×Piout : 1.1 k/spill



KPinon-bias= Kin×Piout : 2.4 k/spill


Kin = 200 k/spill
Piin = 70 k/spill
W/o Forward veto
2nd level trigger : Ge hit


Ge OR (one of Ge detector has hit)
Vetoed : Overflow of all ADC data
⇒KPi trigger was reduced to 28%.
⇒Trigger rate : 0.31 k/spill
48D48 acceptance

60 msr

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