status and expected performance of the lhcb experiment pascal perret laboratoire de physique...

Status and Expected Performance of the LHCb

ExperimentPascal PERRET

Laboratoire de Physique Corpusculaire Clermont-FerrandUniversité Blaise Pascal – CNRS/IN2P3

France

On behalf of the LHCb Collaboration

6th International Conference on Hyperons, Charm and Beauty Hadrons Chicago

3rd July 2004

2P. Perret 3rd July 2004 Beach 2004

OUTLINE

Introduction: Physics motivationLHCThe LHCb experiment

Status of the experimentTrigger

Physics prospectsMeasurement of angle

Summary and conclusions

Introduction: Physics motivationLHCThe LHCb experiment

Status of the experimentTrigger

Physics prospectsMeasurement of angle

Summary and conclusions


SM predicts large CP violating asymmetries SM predicts large CP violating asymmetries for B mesons, in many (often rare!) decaysfor B mesons, in many (often rare!) decays

LHCb: dedicated b physics precision experiment of 2nd generation to study CP violation and rare b-decays

Much higher statistics Access to all b-hadron species: Bd, Bu, Bs, Bc, Λb , … Overconstrain the unitarity triangles

(consistency checks) Search for New Physics beyond the

SM

Physics motivation of LHCb

Unitarity TrianglesUnitarity Triangles

Bd0

Bd0

BS0 DS

Bd0 J/ KS

0

BS0 J/

Bd

Bs

New particles may show up in loop diagrams, overconstrain will allow to disentangle SM components from the new-physics ones

NP?NP?b

d d

b

t

t

High statistics is mandatory

VudVub VtdVtb

VcdVcb

* *

*Bd

0 DK*0

BS0 DSK

Bd0 D*

VtbVub

VtdVud

VtsVus

**

*


Advantage of LHC

LHC startup in spring 2007LHC startup in spring 2007 pp collisions at √s = 14 TeV, f=40 MHz, multiple pp

interactions/bx Clear objective is to get to 1033 cm-2 s-1 during 2007 operation Increase luminosity to 1034 cm-2 s-1 in the next few years total ~ 100 mb, visible ~ 65 mb, bb~ 500 µb, bb/ visible = 0.8% Forward production of bb, correlated

LHCbLHCb Single arm spectrometer

12 mrad <θ< 300 mrad (1,9<η<4,9) <L>LHCb = 2 x1032 cm-2 s-1 (tunable: controlled beam focus at LHCb IP) Efficient trigger and clean events

100b230b

~1012 bb events per year (107 s) with nominal LHCb luminosity at LHC start-up

_


LHC

Geneva

CERN


LHCTI8 - MBIT

TI8 - MBIBVQRL

Dipoles> 300/1200 delivered

Transfer line installed (2.6 km) 1st beam October

Short Straight Sections


LHCb Requirements

Efficient trigger for many B decay topologies Leptonic final state → Muon

system, ECAL + Preshower Hadronic final state→HCAL High pt-particles with large

impact parameter→VELO,TT Efficient particle identification

π/K separation (1<p<100GeV) → RICH

Good decay time resolution→ VELO

Good mass resolution→ Tracker and Magnet

Bd K*BdJ/

HIGH STATISTICS


LHCb detector

VertexVertex

LocatorLocator

TrackingTracking

StationsStations

RICH IIRICH II

HCALHCAL

MuonMuon

StationsStations

RICH IRICH I

SPD/PSSPD/PS

ECALECAL

MagnetMagnet

TriggerTrigger

TrackerTracker

20 m

Forward spectrometer (running in pp collider mode)

Construction

Construction

well progressing

well progressing

Construction

Construction

well progressing

well progressing


LHCb status: Vertex Locator

21 stations, retractable during injection sensitive area starts at only 8 mm from beam axis r/φ sensors (single sided, 45º r-sectors) pitch ranges from 35 μm to 102 μm 200 μm thin silicon 180k readout channels

Vertex AND Tracking detector

VELO mechanics

2 halves in a “Roman-pot”

PV resolution: ~8μm (x,y) and ~44μm (z) IP precision: ~40μm

1m

sensors


LHCb status: Tracking system

Tracking system and dipole magnet to measure angles and momenta:

Magnetic field regularly reversed to reduce experimental systematics

dp/p ~ 0.37 %, mass resolution ~ 14 MeV

(for Bs DsK) tracking efficiency ~ 94%

(for p>10 GeV)


Magnet Warm Al conductor 4 Tm integrated field Weight = 1500 tons 4.2 MW

Assembly of yoke completed Moving magnet into final

position (July 04) Field map measurements

(2004-2005)


Tracking chambers (TT, IT, OT)

TTrigger rigger TTrackerracker

•Level-1 trigger•KS, low-p tracks

IInner nner TTrackerracker

OOuter uter TTrackerracker 3 stations with 4 double layers 5mm straw tubes 50k readout ch.

3 stations with 4 layers each

198 μm readout pitch 130k readout ch. 1.3% of sensitive area → 20% of all tracks

2*2 layers 410 μm silicon 198 μm r/o pitch 144k readout ch.

beam pipe

320 µm thick sensors410 µm thick sensors

TT

IT

OT T1 to T3

~1.4x1.2 m2

~6x5 m2

~1.2x.4 m2


Tracking chambers (TT, IT, OT)

OOuter uter TTrackerracker 3 stations with 4 double layers 5mm straw tubes 50k readout ch.

Production started

OT


RICH

Provide > 3 σ π–K separation for 3 < p < 80 GeV

Two RICH detectors for charged hadron identification

Bs K+K-

p=84%ε=79%

p=13%

Aerogel and C4F10

CF4

RICH-1:25-300 mrad

RICH-2:15-120 mrad

ε(K→K)=88%; ε(π→K)=3%


RICH

RICH2 super structure ready

Photon detector:Hybrid Photodiodes (1024 pixels- LHCb development) orderedRICH 1 : 168 HPDRICH2 : 262 HPD

Exit/entrance windows ready

80 mm


Calorimeter: SPD,PS,ECAL,HCAL

e

h

Identification: electrons, hadrons and neutrals (γ,π0) Readout every 25 ns (L0 trigger) SPD,PS (2.5X0), ECAL(25X0):

5962 channels (Pb/scintillator)

HCAL(5.6λ): 1468 channels (Iron/scintillator)

σm(π0γγ)

~ 10 MeV/c2

2 resolved clusters

(2 merged clusters: ~ 15 MeV/c2) ECAL: E/E =8.3%/E 1.5%HCAL: E/E =75%/E 10%

(ee) = 95%, (e) = 0.7%

Conversion


SPD - PS

PS/SPD modules: ~ 25% completed Assembly SuperModules: start September

200 64APMT


ECAL - HCAL

HCAL modules: ~ 60% completed Installation start December

ECAL modules: 100% completed Installation start November (shashlyk type)


Muon System

µ id. efficiency ~ 94% for pion misidentification rate <~1%

1380 MWPC chambers Chambers in M2-M5:

4 layers in M1: 2 layers

x and y projectivity to Interaction Point

435 m2

26 k readout channels hadron absorber thickness of 20

Muon identification, also used in first level of trigger


Muon SystemFoam Panel Production Automated wiring

machine

Final chamber assembly

Production started

5 sites

~5% ready


Trigger

bb ~ 500 b, < 1% of inelastic cross-section Use multi-level trigger to select interesting

events: high pT electrons, muons or hadrons vertex structure and pT of tracks full reconstruction

~ 200 Hz to tape

30–60%efficiency

HCAL trigger dominates

MUON trigger dominates

ECAL trigger dominates

L0 L1 HLT

µ: pT >1.1 GeVe: ET >2.8 GeV ET >2.6 GeV

h: ET >3.6 GeV


1 MHz

40 kHz

200 Hz output

Level-1:Impact parameter

pT ~ 20%

HLT:Final state

Reconstruction

CalorimeterMuon Pile-up

VertexTrigger TrackerLevel-0 objects

Full detectorInformation

Level-0:Level-0:ppTT of of

, e, h, , e, h,

µsµs

1 ms1 800 CPU

L0 = synchronized hardware trigger

commercial hardwareflexible (L1↔HLT)scalable → easy upgrade

Trigger40 MHz

asynchronousSW trigger


Simulation• MC Pythia 6.2 tuned on CDF and UA5 data, QQ, GEANT3• Multiple pp interactions and spill-over effects included

• Complete description of material from TDRs• Individual detector responses tuned on test beam results

• Complete pattern recognition in reconstruction: without using MC true information

• 2003: 67M events produced• 10M inclusive bb events (4 mn of data taking!)• Used for expected physics performance quoted here

• 2004: 180M events simulation and analysis in a distributed way (Grid)• Started in May (already ~50M events produced), 3000

jobs/day• Pythia, EvtGen, GEANT4

TT

T1 T2 T3

VELO MagnetRICH1


Efficiencies, event yields and Bbb/S ratios

Nominal year = 1012 bb pairs produced (107 s at L=21032 cm2s1 with bb=500 b)Yields include factor 2 from CP-conjugated decaysBranching ratios from PDG or SM predictions


The ‘gold plated’ channel at B-factories Precision measurement of this parameter is very

important

from B0 J/ Ks

=0 in SM =sin 2

In one year with 240k events: sin sin 0.02 0.02

Comparing with other channels may indicate NP in penguin diagrams

Background-subtracted BJ/()KS CP asymmetry after one year

=37%tag=45%

eff≈3%

B/S=0.8 LHC(b) will bring a lot of

statistics to this channel, which can be used to look into higher order effects, and fit Adir

Similar sensitivity ATLAS/CMS


mmss from BsDs-(KK)+

If NP is present …

Expected unmixed Bs Ds sample

in one year of data taking (fast MC)

Fully reconstructed decay:Excellent momentum resolution,

decay length resolution ~200 µm Proper time resolution ~40fs

=30%tag=55%

eff≈9%

B/S=0.3

In one year with 80k events: can observe >5 oscillation signal if ms < 68 ps1

well beyond SM prediction (14.8-26 ps1)

Once a Bs–Bs oscillation signal is seen, the frequency is precisely determined: (ms ) ~ 0.01 ps-1ATLAS/CMS: ms < 30 ps1


from Bs

J/

Is not CP eigenstate (VV decay). Angular analysis needed to separate CP-even and CP-odd contributions (from transversity angle distribution): needs fit to angular distributions of decay final states as a function of proper-time (good proper-time resolution is essential)

In one year with 120k events:

sin sin 0.06 0.06 , ssss 0.02 0.02

In SM expected asymmetry sin 2very small ~ 0.04 sensitive probe for new physics

Reconstruct J/ or ee, KK

Bs counterpart of the golden mode B0 J/ KS

measures the phase of Bs mixing


from B and BsKK

In both decays large b d(s) penguin contributions to b u

Measure time-dependent CP asymmetries in B and BsKK decays:

ACP(t)=Adir cos(m t) + Amix sin(m t)

Exploit U-spin flavour symmetry for P/T ratio [Fleischer] Use measure of from B0 J/ and ffrom B0 J/ Ks

4 measurements (CP asymmetries) and 3 unknowns (, d and ) can solve for

Good /K identificationB

In one year :

degdeg

U-spin symmetry assumed; sensitive to new physics in penguins

BsKK

37 kBbb/S=0.3

26 kBbb/S<0.7


A3

√2 A2

from B DK* and B DK*

B DCPK*: interference between 2 tree diagrams Application of Gronau-Wyler method [Dunietz]:

In one year :

degdeg

Measure 6 decay rates (following three + CP-conjugates)A1 = A1

√2 A2 A3

2

yield/yr

B/S

B D0 (K+) K*(K+)

0.5k <1.8

B D0 (K+) K*(K+)

3.4k <0.3

B DCP (KK) K*

(K+)0.6k <1.4=65o, =0

No proper time measurement or tagging required

assumes DCP = (D + D )/2

sensitive to new phase in DCP

state


from Bs Ds K+

Interference between 2 tree diagrams (again) via Bs mixing Measure -2 from time-dependent rates:

BsDs K (b c) and BsDs

K (b u) (+ CP conjugates) Use 2 from Bs J/

Mistag extracted from Bs Ds sample

5.4 kB/S<1

Bs Ds π is background for Ds KBranching ratio ~ 12 higher

In one year :

degdeg

No theoretical uncertainty; insensitive to new physics in B mixing

The two Bs-Bs asymmetriesafter 5 years of data


1. BBs s D DssKK 2. B B , B, Bss KK KK 3. B B DK* DK*

not affected by not affected by new physicsnew physics

affected by affected by possiblepossible

new physics in new physics in penguinpenguin

affected by affected by possible possible new physics innew physics inD-D mixingD-D mixing

Determine the CKM parameters A,,,

independent of new physics

Extract the contribution of new physics to the

oscillations and penguins

New physics in angle measurement ?

Interest in over-constraining the CKM UT


Other physics at LHCb New physics in b s penguin processes

B0 K*, B0 KS ,Bs KK, … Bs

0 J/Bs0 J/, , …

Direct CP violation: Bu K*

Rare decays Bs ,B0

d K*0(cf talk from S. Viret)

Bc physics Lifetime, mass, branching fractions

measurements from Bc D Ds difficult!

b baryons …


Conclusion LHCb is dedicated to the study of b physics

a devoted trigger excellent vertex and momentum resolution excellent particle identification Access to all b-hadron species: Bu, Bd, Bs, Bc , b …

LHCb detector will be ready for data taking in 2007 at LHC start-up Construction of the experiment is progressing well installation of detectors starts this year

Already in year one, LHCb will have competitive measurements on mmss and other parameters

LHCb offers an excellent opportunity to spot New Physics signals beyond the Standard Model very soon at LHC


Are Penguins New Physics Guards?

status and expected performance of the lhcb experiment pascal perret laboratoire de physique...

Documents

n overconstrain

d s b d

physics motivation n

rare bdecays n

b mesons

conclusions n introduction

outline n introduction

n pp collisions