b – физика на LHCb

А.И. Голутвин (ИТЭФ)

Нарушение Редкие распадыCP чётности

LHCb – forward spectrometer (running in pp – collider mode) Data taking starts next year

Expect ~10 fb-1 by 2013 B physics is also a part of the ATLAS and CMS early program

LHCb is designed to run at an average luminosity of 2 1032 and be able to handle 51032 cm-2s-1 for short periods

For a “nominal” year of 107 seconds this corresponds to 2 fb-1 . Most physics

goals are expressed in terms of the reach for 10 fb-1 (i.e. 5 nominal years)

Super LHCb (SLHCb) will run at 10 times the initial design luminosity with twice more efficient trigger

and record data sample of > 100 fb-1 Start data taking after 2014

Working Group set up to identify the R&D required to make an upgrade of LHCb feasible, and to make the physics case

Issues of triggering, fast vertex detection, electronics, radiation dose, handling the pile-up and higher occupancy, etc…→ Expression of Interest for R&D towards an upgrade is in preparation

LHCb Collaboration

LHCb is a collaboration of ~ 670 members from 48 institutes

– in Brazil, China, France, Germany, Ireland, Italy, Poland, Romania, Russia, Spain, Switzerland, Ukraine, UK, and the US

Российские Институты:

ИТЭФ(Москва), ИФВЭ(Протвино), ИЯИ(Троицк), ПИЯФ(Гатчина), ИЯФ(Новосибирск) внесли определяющийвклад в создание калориметрической системы имюонного детектора

Планируется вступление в коллаборацию НИИЯФ МГУ

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The LHCb Experiment

p

p

Interaction point

Dipole magnet

10 – 300 mrad forward acceptance

Forward geometry

Running with less focused

beam is sufficient

At 21032 1012 bb pairs

are produced per year

Experimental infrastructure

Shielding wall(against radiation)

Electronics + CPU farm in barracks(Control Room on surface)

Offset interaction point To maximize space

Most detectors opentransversely for access

Shielding wall

• Upper part completed

• Assembly of lower part is progressing wellPaused while a problem with leaking

cooling-water pipes is investigated

Labour intensive “Egyptian work” as inaccessible by crane…

It’s full!Installation of major structures is essentially complete

Commissioning is ongoing !

Muon detector

Calorimeters

RICH-2

Magnet

OT

VELO

RICH-1

UT as a standard approach to test the consistency of SM

Mean values of angles and sides of UT are consistent with SM predictions

Accuracy of sides is limited by theory:

- Extraction of |Vub|

- Lattice calculation of

Accuracy of angles is limited by experiment:

= ± 13° = ± 1° = ± 25°

Search for NP comparing observables measured in tree and loop topologies

(tree+box) in B J/Ks (tree) in many channels(tree+box) in Bs J/

(peng+tree) in B,, (peng+box) in BKs (peng+box) in Bs

New heavy particles, which may contribute to d- and s- penguins,could lead to some phase shifts in all three angles:

(NP) = (peng+tree) - (tree)

(NP) = (BKs) - (BJ/Ks) ≠ 0 (NP) = (Bs) - (BsJ/)

Contribution of NP to processes mediated by loops (present status)

to boxes:

vs |Vub / Vcb | is limited by theory (~10% precision in |Vub|) (d-box)

not measured with any accuracy (s-box)

to penguins:

((NP)) ~ 30° (d-penguin) ((NP)) ~8° (s-penguin) ((NP)) not measured (s-penguin)

PS (NP) = (NP) (NP) measured in B and B decays may differ depending on penguin contribution to and final states

Search for NP comparing observables measured in tree and loop topologies

: LHC prospects

In SM S = - 2arg(Vts) = - 22 ~ - 0.04

Sensitive to New Physics effects in the Bs-Bs system if NP in

mixing S = S(SM) + S(NP)

2 CP-even, 1 CP-odd amplitudes, angular analysis needed to separate, then fit to S, S, CP-odd fraction

LHCb yield in 2 fb-1 131k, B/S = 0.12

Bs J/ is the Bs counterpart of B0J/ KS

will reach s(s) ~ 0.08 (10/fb, ms=20/ps, 90k J/ evts)

LHCb

ATLAS

0.021

0.021

Vcs* Vub: suppressedFavored: Vcb Vus

*

b

u

s

u u

b

u

cD(*)0

K(*)-

B-

u

s

u

c

D(*)0

f

Common

final state

K(*)-

B-

Interference between tree-level decays

iiBKDBA

KDBA eer B

0

0 Parameters: γ, (rB, δB) per mode

Three methods for exploiting interference (choice of D0 decay modes):

(GLW): Use CP eigenstates of D(*)0 decay, e.g. D0 K + K- / π+π– , Ksπ0

(ADS): Use doubly Cabibbo-suppressed decays, e.g. D0 K+π -

(Dalitz): Use Dalitz plot analysis of 3-body D0 decays, e.g. Ks π+ π-

Mixing induced CPV measurement in Bs Ds K decays Specific for LHCb

UT angle : LHCb (BaBAr & BELLE & Tevatron ~12° precision for at best)

LHCb status report

B± → D(KSπ+π−) K±

• Mode used by B factories to give best existing constraint on CKM angle :

[BaBar] 12114192[Belle] 9 3 53 15

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B+(stat, syst, model) B

~ 400 events each

• LHCb yield ~ 5000 events/2 fb-1

• Spot the difference between the Dalitz plots for B+ and B → effect of CP violation

• Binning can reduce model dependence

Precision on ~ 12º (in one year)

Simulated data for LHCb (1 year)hep/ph 0703267

Model-independent approach

A.Bondar, A.Poluektov Eur.Phys.J C47,347(2006) hep-ph/0510246

50 ab-1 at SFF factory should be enough for model-independent γ/φ3 measurement with accuracy below 2°

1fb-1 at ψ(3770) corresponds 2100 CP-tagged KS+ - events (first estimation based on CLEO-c data by David Asner)

~10 fb-1 at ψ(3770) needed to accompany SuperB measurement

angle ( 3 ) at SFF

Combined precision after 2 fb-1 () 5 (from tree only)

UT angle : LHCb summary table

LHCb (10fb-1 ) and SFF (50-75 ab-1) & SLHCb (>100 fb -1) sensitivities

LHCb

SFF & SLHCb

Channel Yield Precision

From tree channels () < 3

Bd +-0

B +0, +-,00 70k45k,10k,5k

() < 4

Bd J/()KS

Bd KS

1200k 4k

(sin2) < 0.01(sin2) ~ 0.1

s Bs J/()Bs

750k 20k

(s) ~ 0.01(s) ~ 0.05

> 2014

SLHCb (stat. only) ~ 0.003 < 1 (BsDsK) - - -

S(K0S) 0.02-0.03

S() 0.01

Search for New Physicsin Rare Decays

Exclusive b s BK* Bs

B hs, sll inclusive

Experimental challenge: keep backgrounds under control

We are just approaching sensitivity promising for discovery…

LHCb

SFF

b s exclusive

LHCb control channel: Bd K* ~75k signal events per 2fb-1

Bs BELLE observed 16±8 events

2 weeks run at (5S); no TDCPV

LHCb annual yield ~11k with B/S < 0.6

b s exclusive

b (L) + (ms/mb) (R)

Measurement of the photon helicity is very sensitive test of SM

Methods: Mixing induced CP asymmetries in Bs , BKs 0 Photon helicity can be measured directly in radiative B decays to final state with 3 hadrons.

Promising channels for LHCb are B K and B K decays

Expected yield per 2 fb-1

BR(B+ K+-+) ~ 2.5 10-5 rich pattern of resonances ~60k BR(B+ K+) ~ 3 10-6 highly distinctive final state ~ 7k

b s exclusive

Mixing induced CP asymmetries

BKs0 (B-factories)

S = - (2+O(s))sin(2)ms/mb + (possible contribution from bsg) = - 0.022 ± 0.015 P.Ball and R.Zwicky hep-ph/0609037Present accuracy: S = - 0.21 ± 0.40 (BaBar : 232M BB) S = - 0.10 ± 0.31 (BELLE: 535M BB)

Bs (LHCb)

LHCb sensitivity with 10fb-1 :

(A) = 0.09

B K*

In SM this bs penguin decay contains right-handed calculable contribution but this could be added to by NP resultingin modified angular distributions

SM

B K*: LHCb prospects

Forward-backward asymmetry AFB (s) in - rest frame is a sensitive NP probe Predicted zero of AFB (s) depends on Wilson

coefficients C7eff / C9

eff

AFB(s), fast MC, 2 fb–1

s = (m)2 [GeV2]

7.2 k events / 2fb-1 with B/S ~ 0.4 After 10 fb-1zero of AFB located to ±0.28 GeV2 providing 7% stat. error on C7

eff / C9eff

Full angular analysis gives better discrimination between models. Looks promising

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Bs

This decay could be strongly enhanced in some SUSY models.

Current limit from CDF BR(Bs) < 4710-9 (2010-9 expected final D0+CDF limit)With loose selection LHCb expects ~40 signal events (2fb-1/SM BR) on top of ~1500 background events (mostly form b , b )

Particle ID, vertexing and invariant mass resolution (M )~ 18 MeV provide excellent separation of signal from background

Very smal BR in SM(3.4 ± 0.5) x 10-9

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OUTLOOK Clean experimental signature of NP is unlikely at currently operating experiments

From now to 2014A lot of opportunities (LHCb will start data taking next year)Important measurements to search for NP and test SM in CP violation : if non-zero NP in boxes < 2010 vs Rb and vs Rt (Input from theory !) (NP) and (NP): if non-zero NP in penguins in Rare decays BR(Bs ) down to SM prediction < 2010 Photon helicity in exclusive bs decays FBA & transversity amplitudes in exclusive bsll decays < 2010

After 2014ATLAS and CMS might or might not discovered New Particles. At the same timeLHCb might or might not see NP phenomena beyond SM.In either case it is important to go on with B physics at SFF & Upgraded LHCb

Need much improved precision because any measurement in b-system constrains NP models

high pTB’s

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LHCb calorimeter system

• Scintillating Pad Detector / PreShower • Electromagnetic Calorimeter• Hadron Calorimeter

Fast response within 25 ns is a 1st priority requirement for L0 trigger All 3 calorimeter are using the “same” technology: absorber/scintillator readout with WLS fibres

Back of SPD

Lead

Front of PS

Andrey Golutvin VCI 2007 26

PS+SPD built from 16 super modules Side view of upper part

Overview of LHCb Overview of LHCb SPD and PSSPD and PS

Inner + Middle + Outer Modules

MAPMT+ VFER/O

cables

Moving cable trays

Scintillator + coiled fiber

Super module frame

Super modulewith 2 x 13 modules

TDR estimations (2000): • outer ~ 20 ph.el. • inner ~ 30 ph.el.

Preshower cosmic test before Super-Module installation # phe/MIP for each tile:

Inner: 25 pheMiddle 29 pheOuter: 19 phe

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Overview Overview of LHCb ECALof LHCb ECAL

3312 shashlik modules with 25 X0 Pb

Scintillators, lead-plates, covers

Fibres with loops

PMT and CW base

Two halves on chariots and electronics platform on top

Chariot

Electron.platform

End-cover

Lead plateScintillator

TYVEK

Front-cover

CW base

PMT

Middle module

Inner module

Outermodule

modules

Beam plug

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Overview of Overview of LHCb HCALLHCb HCAL

particles

PMT

scintillators

fibers

light-guide

Internal cabling

CW base

PMT housingModule with optics assembled

Electron.platform

Chariot

52 modules with longitudinal tiles

modules

Beam plug