prospect for Bc->BsPi II (Bs->DsPi)
description
Transcript of prospect for Bc->BsPi II (Bs->DsPi)
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