prospect for Bc->BsPi II(Bs->DsPi)

tomoyo fukami

@BMLCPV(2008/7/29)

目次

• method

• signal & background

• cut

• plot

• backgound estimation

• conclusion

method• mode

– Bc->BsPi->DsPi->PhiPi– Bc->BsPi->DsPi->K*K– Bc->BsPi->DsPi->3Pi

• using momentum and vtx , reconstruct track(K,Pi) in order of Ds mass -> Bs mass ->Bc mass

• data （ signal : MC 　 and 　 bkg : Data (two track trigger) ）

signal & background

• signal : Bc->BsPi

• bkg : – Bc->Bslνπ– Bc->Bs*π->Bsγ– Bc->BsK– P.V. Bs+π– fake Bs

→use sideband data for bkg

Bc Branching 　 Fluction

cut parameters

• pre selection

Philipp Mack ph.D thesis IEKP-KA/2007-10(2007)

cut parameters

• BOX cut

Bc->BsPiplots

PhiPi3Pi

K*K

only Vtx construct required

pre 　 selection

cut base

PhiPi

3σ

3Pi

consideration• we estimated the numb

er of signal and background (asBc,Bs*Pi,other) in signal window.

M(Bc)-M(Bs) gauss fit

K*K

mean±3σ: signal window

asBc background 1

PhiPi3Pi

K*K

after pre selection cut

asBc : PV Bs but able to reconstruct Bc combinatoraliy with a pion in fragme

ntation.

asBc background 　２

PhiPi3Pi

K*K

after BOX cut

asBc : PV Bs but able to reconstruct Bc combinator

aliy with some pion.

calculation of n(expected)after pre selection cut

• Philipp Mack ph.D thesis IEKP-KA/2007-10(2007)

を用いた。

　　

）σ（）σ（

）σ（

）σ（

)1)(@3(36551),*(34711),(461505

164.0)(

047.0

)(

)()(

1

exp

fbPiKKPhiPin

BsBcBR

BsXpp

BcXpp

n

n

BsBRBsXpp

BsBRBsBcBRBcXpp ected

BOX

Bs

BOX

Bc

εis obtained from MC

how many events (Bc->BsPi)are obser

bed ?

and how many events (asBc bkg)are obs

erved?

mode signal[event]

bkg(pre)[event]”asBc”

bkg(pre)[event]”Bs*Pi”

bkg(pre)[event]”other”

PhiPi 15.3±2.44 3.8*10^-5 1.9*10^-6 1.2*10^-3

K*K 6.48±1.07 2.14*10^-5 1.6*10^-6 8.2*10^-4

３ Pi 4.28±0.90 2.69*10^-5 2.6*10^-7 1.3*10^-4

the number of event in signal window

conclusion

• The “asBc” background is enough small after applying pre selection cut

• Bc->BsPi :”asBc” type background event is nearly negligible in DsPi mode.

plan• estimation of other combinatorial background.• To reject combinatorial background using NN(well known).

•we checked the efficiency of the BOX cut of Bc->BsPi->DsPi->PhiPi(,K*K,3Pi).

•we estimated the effect of “asBc” type background after applied by pre selection -> negligible

•we estimated the effect of “BsX” type background after applied by preselection -> negligible

• combinatorial background looks dominant

summary

buck up

consideration

• signal Bc の mass window での asBc(bgd)の割合について

mean sigma signal window （ ±3σ ）

PhiPi 9.20*10^-1

(±5.96*10^-1)

7.24*10^-3 (±7.24*10^-3)

0.90-0.94

K*K 9.20*10^-1

(±5.54*10^-1)

7.39*10^-3 (±7.88*10^-3)

0.90-0.94

3Pi 9.20*10^-1

(±5.54*10^-1)

6.58*10^-3 (±6.58*10^-3)

0.90-0.93

M(Bc)-M(Bs)の

gauss fit

＊出来ればプロットと、パラメータを ROOT で出力

ss

• signal に関与しない領域（ sideband ）のData をもちいて back ground とする。

back ground について

signal sideband

introduction

• QCD, EW 　の良いテストベンチ (quarkonium 以外で唯一の heavy quark ふたつから成る粒子 )

• QCD 計算モデルの検証（特にクオークの束縛状態モデルや、重いクオーク系での有効理論の検証）– 質量– 寿命　 etc…

• 各終状態への相対崩壊分岐比– 理論の検証や上記物理量の抽出に重要。– 理論予測では Bc->BsX 　に次いで大きな分岐比を持つが、未発見

• Bs 振動や CP 位相安定性の測定に用いる、 Bs フレーバー同定のための Bs 寿命測定への影響を正しく考慮できる

asBc background

asBc : PV Bs but able to reconstruct Bc combinatoraliy with a pio

n in fragmentation.

PhiPi3Pi

K*K

after pre selection cut