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) W/o S (K-, p-) reaction : True trigger 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+g (100%)⇒L→ p+p- (64%), n+p0 (36%) p(K-, p-)S+ : S+→ p+p0 (52%), n+p+ (48%) p-やp0→2g, gがGeにhit ⇒おおよそ生成量とHyperball-J acceptanceで量が決まる HBJ acceptance ~30%程度 (target内部等方生成), (p0→2g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、 gを出す Quasi-free反応で標的の原子核に励起状態ができ、それがg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…)

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

4LHe 反応を羅列 True : 4He(K-, p-)4LHe ⇒ 4LHeのdecay Quasi-free production g-decay : 4LHe*→4LHe+g 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

7LLi, 10LB, 11LB, 19LF (+ 12LC, 16LO) 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 g放出 ⇒ gによるGe trigger 核子放出 ⇒ 周辺物質からのbackground g 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 Kin = 200 k/spill Piin = 70 k/spill KPinon-bias= Kin×Piout : 2.4 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