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Sheldon Stone Syracuse Univ. LHCb. The L arge H adron C ollider b eauty Experiment & Physics. General Physics Justification. Expect New Physics will be seen at LHC Standard Model is violated by the Baryon Asymmetry of Universe & by Dark Matter Hierarchy problem (why M Higgs <<M Planck )

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Lhcb

Sheldon Stone

Syracuse Univ.

LHCb

The Large Hadron Collider beauty Experiment & Physics


General physics justification

General Physics Justification

  • Expect New Physics will be seen at LHC

    • Standard Model is violated by the Baryon Asymmetry of Universe & by Dark Matter

    • Hierarchy problem (why MHiggs<<MPlanck)

  • However, it will be difficult to characterize this physics

  • How the new particles interfere virtually in the decays of b’s (& c’s) with W’s & Z’s can tell us a great deal about their nature, especially their phases

Aspen Winter Conference, February, 2006


Example

  • Contributions to direct CP violating decay

B-fK-

Asym=(MW/msquark)2sin(fm), ~0 in SM

Example

  • MSSM from Hinchcliff & Kersting (hep-ph/0003090)

  • Contributions to Bs mixing

BsJ/yh

CP asymmetry  0.1sinfmcosfAsin(Dmst), ~10 x SM

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Limits on new physics from b s

cl>90%

cl>5%

cl>32%

s

h

From Perez

Limits on New Physics From b’s

  • Is there NP in Bo-Bo mixing?

  • Assume NP in tree decays is negligible

  • Use Vub, ADK, SyK, Srr, Dmd, ASL

  • Fit to h, r, h, s

  • For New Physics via Bdo mixing, h is limited to ~<0.3 of SM except when sBd is ~0o or ~180o of SM decays

  • New physics via Bs mixing, or bs transitions is unconstrained

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Most currently desirable modes

Most Currently Desirable Modes

  • BS mixing using BSDS+p-

  • High Statistics Measurement of forward-backward asymmetry in B K*m+m-

  • Precision measurements of CP ’s

    • CP violating phase in BS mixing using BSJ/yf

    • g (or f3) Using B- DoK- tree level decays

    • g using BSDS+K- time dependent analysis

    • a especially measurement of Bo roro

    • b at high accuracy to pin down other physics

  • CPV in various rare decay modes

  • B(S) m+m-

  • Important: Other modes, not currently in vogue

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Detector requirements general

Detector Requirements - General

  • Every modern heavy quark experiment needs:

    • Vertexing: to measure decay points and reduce backgrounds, especially at hadron colliders

    • Particle Identification: to eliminate insidious backgrounds from one mode to another where kinematical separation is not sufficient

    • Muon & electron identification because of the importance of semileptonic & leptonic final states including J/y decay

    • g, po & h detection

    • Triggering, especially at hadronic colliders

    • High speed DAQ coupled to large computing for data processing

    • An accelerator capable of producing a large rate of b & anti-b hadrons in the detector solid angle

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Basics for sensitivities

Basics For Sensitivities

  • # of b’s into detector acceptance

  • Triggering

  • Flavor tagging

  • Background reduction

    • Good mass resolution

    • Good decay time resolution

    • Particle Identification

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The forward direction at lhc

Pythia production cross section

100 mb

230 mb

The Forward Direction at LHC

  • In the forward region at LHC the bb production s is large

  • The hadrons containing the b & b quarks are both likely to be in the acceptance

  • LHCb uses the forward direction, 4.9 > h >1.9, where the B’s are moving with considerable momentum ~100 GeV, thus minimizing multiple scattering

  • At L=2x1032/cm2-s, we get 1012 B hadrons in 107 sec

pT

h

Production

 Of B vs B

q B (rad)

q B (rad)

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The lhcb detector

The LHCb Detector

Muon Detector

Tracking

stations

proton

beam

interaction

region

Trigger

Tracking

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The velo

Geometry

R sensor: 38 mm pitch inside to

103 mm outside

f sensor: 39 mm pitch inside to

98 mm outside

1 m

R

sensors

f

sensors

3 cm separation

Interaction point

The VELO

Sensor

Half

Vacuum

Tank

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Triggering

Triggering

  • Necessary because b fraction is only ~1% of inelastic cross-section

  • At peak luminosity interaction rate is ~10 MHz, need to reduce to a few kHz. The B hadron rate into the acceptance is 50 kHz

  • General Strategy

    • Multilevel scheme: 1st level Hardware trigger on “moderate” pTm, di-muons, e, g & hadrons, e.g. pTm >1.3 GeV/c; veto on multiple interactions in a crossing except for muon triggers.

    • Uses custom electronics boards with 4 ms latency, all detectors read out at 1 MHz

    • Second level and Higher Level software triggers

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Software triggers

Software Triggers

  • Second Level: All detector information available. Basic strategy is to use VELO information to find tracks from b decays that miss the main production vertex; also events with two good muons are accepted & single muon with pT > 2.1 GeV/c. Strategies are constantly being improved.

  • Higher Level Triggers: Here more sophisticated algorithms are applied. Both inclusive selections and exclusive selections tuned to specific final states done after full event reconstruction has finished. Output rate is ~2 kHz

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Trigger output

Trigger Output

  • Rough guess at present (split between streams still to be determined)

  • Large inclusive streams to be used to control calibration and systematics (trigger, tracking, PID, tagging)

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Trigger monitoring

Trigger Monitoring

  • Trigger lines need constant monitoring to adjust prescales, especially at beginning of experiment.

  • General approach: for a particular trigger

    • Define TOSTrigger On Signal

    • Define TIS Trigger Independent of Signal

    • Efficiency =(TISTOS )/TIS

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Trigger monitoring example

Trigger Monitoring Example

  • Comparison of L0 trigger efficiency on muon tracks that miss the IP as a function of Pt for both “traditional” Monte Carlo method & (TISTOS )/TIS

  • Can be done quickly with real data

TIS & TOS

Method

Traditional MC

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Flavor tagging

Flavor Tagging

“opposite side”

  • For Mixing & CP measurements

    it is crucial to know the b-flavor

    at t=0. This can be done by

    detecting the flavor of the other B

    hadron (opposite side) or by using

    K± (for BS) p± (for Bd) (same side)

  • Efficacy characterized by eD2, where

    e is the efficiency and D the dilution = (1-2w)

  • Several ways to do this

“same side”

eD2 (%)

Not exactly

same cuts as table

Expect eD2 ~ 7.5% for BS & 4.3% for Bd

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Background reduction using s t

Background Reduction Using st

  • Excellent time resolution ~40 fs for most modes based on VELO simulation

  • Example

    BS mixing

Bs→Ds-π+

100 mm

Bs→Ds-π+(tagged as Bs)

10 mm

LHCb can measure DmS up

68 ps-1 in 2 fb-1

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Background reduction from particle id

CDF data

Bd signal

Background Reduction from Particle ID

  • LHCb has two RICH detectors. Most tracks in range 100>P>2 GeV/c. Tagging kaons at lower momentum < 20 GeV/c; Bh+h- up to 200 GeV/c, but most below 100 GeV/c

  • Good Efficiencies with small fake rates

Excellent

mass resolution

s=14 MeV

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The rich detectors

80 mm

The RICH Detectors

HPD Photon Detectors

RICH I Design

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Rich ii

RICH II

RICH2 –installed in the pit

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Cp asymmetry in b s j f

CP Asymmetry in BSJ/ f

  • Just as BoJ/ KS measuresCPV phase bBSJ/ f measures CPV BS mixing phase fS

  • Since this is a Vector-Vector

    final state, must do an angular

    (transversity) analysis

  • The width difference DGS/GS

    also enters in the fit

  • LHCb will get 120,000 such

    events in 2fb-1. Projected errors are ±0.06 in fS & 0.02 in DGS/GS (for DmS = 20 ps-1)

  • Including BSJ/ h, will increase sensitivity (only 7K events)

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Neutral reconstruction

Merged 0

Resolved 0

Neutral Reconstruction

  • Mass resolution is a useful s=~6 MeV

  • Efficiency within solid angle is OK using both merged and resolved po’s

  • Example: time dependent Dalitz Plot analysis ala’

    Snyder & Quinn for Borp p+p-po

  • 14K signal events in 107 s with S/B 1/3, yielding s(a)=10o

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Other physics sensitivities

Other Physics Sensitivities

  • Only a subset of modes

  • For ~1 year of running

Zero to ±0.04 GeV2

Afb

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Status

Status

  • Magnet installed

    & mapped

  • ECAL, HCAL, RICH II

    & Muon Filter Installed

  • Construction on all

    other items proceeding

  • Software is progressing

  • New MC-data challenges using Grid

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Overview

Overview

Overall in very good shape for startup in 2007

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View of pit

Muon system

-iron shielding

-electronics tower

Calorimeter-E-cal, H-cal modules

RICH2

Magnet

RICH1

-HPD shielding box

OT: straw module production completedMuon: more than half of chambers produced

View of Pit

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Possible improvements

Bop+p-

BSfg

BSJ/yf

BSDSK-

Possible Improvements

  • Run at higher luminosity.

    Increase to 5x1032 /cm2-s

  • Gains in event yields,

    especially dimuon modes

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Possible upgrades

Possible Upgrades

  • VELO needs to be replaced after ~6-8 fb-1 due to radiation damage

    • Are considering hybrid Silicon pixels as a replacement

    • Since they are much more rad hard than current VELO, we could move closer to the beam getting better vertex s

    • These could possibly allow some vertexing in first trigger level with minor modifications

  • EM calorimeter upgrades such as having a central PbWO4 region

  • Major modifications to readout including long digital pipelines that would enable extensive 1st level vertex triggering and allow higher luminosity running (very expensive)

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Conclusions

Conclusions

  • LHCb will study CP Violation and Rare Decays in the BS, B-, & Bd systems at an unprecedented level of accuracy

  • These studies are crucial for specifying any new physics found directly

    at the Tevatron or LHC

  • LHCb is on schedule

  • LHCb is starting to think

    about upgrades

From Hewett & Hitlin

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The end

The End


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