Rare Decays

sB

sB

00 KB

and their sensitivity to New Physics

320

22/1

422/1

66 )(GeVtan10

)(

MMM

BB s

Klassiker: sB

hep-ph/0108037

-9100.4)3.4(BR :SM mSUGRA Parameter:

sign,tan,)(,, 002/1 AMMM A

Light chargino bounds from LEP, Radiative EWSB

LSP not neutral hep-ph/0108037

320

22/1

422/1

66 )(GeVtan10)( MMMBB s

< 5.8·10-8 95% CL

2 fb

-1arXiv:0712.1708 to PRL

< 9.3·10-8 95% CLD0 Note 5344-Conf (2007)

Problem:

Untergrundunterdrückung

0B

B

Invariante Masse keine ausreichende Diskriminate

Multivariate Analyse

Lifetime of B

Muon Impact Parameter Sign.

Bs Impact Parameter

DOCA between muons

Isolation

Geometry Likelihood

Muon Pion Likelihood (LL)

Muon Kaon Likelihood (LL)

PID Likelihood

signalbb inclusiveb b BcJ/

M

signalbb inclusive

3-dim. Binning:

• 4 Bins in Geometry LL

• 3 Bins in PID LL

• 5 Bin in invarianter MasseMeV18

Untergrund Ereignisse/Bin

Signalereignisse/Bin (BR)

Sensitivität

BR excluded at 90 % CL, i.e. only background is observed BR observed or discovered.

Exclude the interesting region between 10-8 and SM with little Lumi (~0.5 fb-1)

Observe (discover) SM BR with 3 (5) after ~2 (~6) fb-1

Events after preselection cuts in 600 (60) MeV mass window

Radiative bs decays

Standard Model bs (bs):

• LH s-quark (RH s-quark)

• LH (RH) photons

BSM physics (SUSY, LR Models) could lead to appreciable RH component photon helicity probes BSM physics

Probing photon helicity:

• (Photon conversion)

• Time dependent ACP:

• Parity-odd triple correlations between photon and 2 out of 3 hadrons in B (K++) decays

b(X)

sB

B0s

[1] hep-ph/0607258 [2] arXiv:hep-ex/0607071v1

Erste Beobachtung von Bs

10)7.5()( 52.1

7.18.15.1

sBBR

510)19.194.3(:SM (Ball et al.)

5.5

sensitive to NPSM NP

polarization predominantly left handed

right handed components

CPV in decay < 1 % 10%-40%

Inclusive decays : theory experimentExclusive decays theory experiment

CPV in interference mixingdecay

B0 (B0bar)X0 very small

B0 (B0bar)X0 Could be large

Why this decay ?

Expected for one year of measurement ( 2 fb-1 )

• have to fight background

• very good PID necessary, 0 rejection

• proper time resolution (Time dependent CPV polarization)

• high trigger efficiency

• good offline selection

What do we expect at LHCb ?

• two body kinematics

• geometrical cuts on pp-interaction PV and B-decay SV

Selection mainly based on

Selection criteria maximize with

=

S: signal evts

B: background evts

SS+B

K-

K+

PV

SV

Reconstruction and Selection

Photon selection

• 2 body kinematics hard ET()

spectrum

• from numerous 0 decay soft

Require ET() > 2.8 GeV

On the way to the

• Charged tracks must NOT

come from PV ( of B)

• K+K- should come from SV

Some selection criteria…

On the way to the B

• pB = ppshould point to PV

• use B ( allow rather large B as the SV resolution is not good because of K’s !)

PV

SV B

reconstructed p

flight path

Some selection criteria…

• large background from B0s und BK*0

use vector meson polarization helicity of for B0

s for B0

s

• define helicity angle H

• sin2H distribution for signals

cos2H distribution for

correlated bkg

flat for combinatorial bkg

K+

K-

B H

Background…

Expect 68k signal events for 2 fb-1 with B/S < 0.6

• red: true events

• blue : comb. bkg.

min13

And finally one gets…

B0 B0

Expect 11.5k signal events for 2 fb-1 with B/S < 0.6

Bs

• from bspredominantly left-handed (SM: V-A

coupling of W boson)

• e.g. in MSSM can be largely right-handed

( doesn’t effect incl. radiative decay rate predicted by

SM)

• helicity measurement via time-dependent CP asymmetry, …

Polarization

Polarization

0)( MtB

R

L

R

L

iL

iR

iR

iL

eAMBA

eAMBA

eAMBA

eAMBA

sin)(

cos)(

sin)(

cos)(

0

0

0

0amplitudes

)()(tan

L

R

MBAMBA

Relative amount of „wrong photon polarization“

LR , Weak phases (CP odd)

Time dependent decay rate

)sin()cos(

2sinh

2cosh))(( 0

tmStmC

tA

teMBB

qq

qqtqq

q

0cos2sinsin2sin CAS

LRM

Standard Model:

12sinA

The CP asymmetry

From the time dependent decay rate one gets

CP Asymmetry

The measurement of Adetermines the fraction of ‘different-polarized’ photons !

LHCb Toy study: 2.0 A for 2 fb-1

B

bb

B mmm

mss ˆ,ˆ

2

00 KB

Asymmetrie:

2M

Interesting observable: Muon forward-backward Asymmetry

„Zero crossing point:“

2ˆ

Bmss

hep-ph/9910221

Generator Studie: 6.5 M Ereignisse.

Change in order to which Wilson coefficients are calculated.

A. Ali et al. hep-ph/9910221

SMSUGRA MIA SUSY

(lower lines = pure short distance components)

M2 mass distributiuon Forward backward asymmetry

SMSUGRA MIA SUSYMIA SUSY C10 >0

Upper/lower lines C7 < 0 / C7 > 0

MIA = Flavor violating SUSY, mass insertion approx.

0B

K

0K

B

0B

K

0K

B

mRMS 33

mRMS 97

%89%95%9310Trigger LL

%3.1%6.20%1.6sel recselrec

totKKBRKBBRS )()(398.0210 00012

61022.1 67.0

Non-resonant background: KBUpper limit: BR < 4 10-7 173075 events / 2 fb-1

irreducible

Asymmetry

In kinematischer Region II erwartet man gleiche Afb wie für K*ll

Q2 Verteilung für Daten-Set von 2 fb-1:

signal

Untergrund (fluktuiert), flach in M

Bemerkung: Nicht-resonanter Untergrund wird vernachlässigt.

Signal Ereignisse: 37001200

Untergund: 1100 250222 GeV94 qm

(non-res ignoriert)

Statistische Signifikanz des Zero-Crossing Punktes:

Kein Untergrund: 0.41 GeV2

Mit Untergrund (kein non-res): 0.46 GeV2 / 0.27 GeV2

Standardmodell: s02 = 4.2 0.6 GeV2

1fb)10(2

Systematische Effekte sind bisher noch nicht untersucht !!

(aus 10000 toy Experimenten)

AFB

s=m2 [GeV2]

2 fb-1

(s0) = 0.46(s0) = 0.27 (10 fb-1)