The status of lhcb
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S. Stone May, 2009. The Status of LHCb. The LHCb Collaboration. 800 Physicists 54 Institutes 15 Countries 1 Group from USA

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The Status of LHCb

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The status of lhcb

S. Stone

May, 2009

The Status of LHCb

American Physical Society, Feb. 16, 2010


The lhcb collaboration

The LHCb Collaboration

  • 800 Physicists

  • 54 Institutes

  • 15 Countries

    • 1 Group from USA

  • Basking in light of 2008 Nobel Prize to Kobayshi & Maskawa, “for the discovery of the origin of the broken symmetry which predicts the existence of at least 3 families of quarks”

American Physical Society, Feb. 16, 2010


Quark mixing the ckm matrix

Quark Mixing & the CKM Matrix

mass

d s b

u

c

m

a

s

s

t

  • A, l, r and h are in the Standard Model fundamental constants of nature like G, or aEM

  • h multiplies i and is responsible for CP violation

  • We know l=0.22 (Vus), A~0.8; constraints on r & h

American Physical Society, Feb. 16, 2010


Current status of cp other measurements

Current Status of CP & Other Measurements

  • SM CKM parameters are: A~0.8, l=0.22, r & h

  • CKM Fitter results using CP violation in J/y KS,r+r-, DK-, KL, & Vub,Vcb& DMq

  • The overlap region includes CL>95%

  • Similar situation using UTFIT

  • Measurements “consistent”

Note: r = r(1-l2/2)

h = h(1-l2/2)

American Physical Society, Feb. 16, 2010


What don t we know physics beyond the standard model

What don’t we know: Physics Beyond the Standard Model

American Physical Society, Feb. 16, 2010


Physics beyond the standard model

Physics Beyond the Standard Model

  • Baryogensis: CPV measurements thus far indicate (nB-nB)/ng = ~6x10-10, while SM can provide only ~10-20. Thus New Physics must exist

  • Dark Matter

  • Hierarchy Problem: We don’t understand how we get from the Planck scale of Energy ~1019GeV to the Electroweak Scale ~100 GeV without “fine tuning” quantum corrections

  • Gravitational

    lensing

    American Physical Society, Feb. 16, 2010


    Flavor problems

    Flavor Problems

    • Why do the fermions have their specific masses? Why are the masses in general smaller than the electroweak scale?

    • Why do the mixing angles (the CKM matrix elements) have their specific values?

    • Is there a new theory that relates the CKM matrix elements to masses?

    • What is the relationship between the CKM matrix and the neutrino mixing matrix?

    American Physical Society, Feb. 16, 2010


    Limits on new physics

    Vcb or Vub

    Limits on New Physics

    • What we observe is the sum of Standard Model + New Physics. How to set limits on NP?

    • Assume that tree level diagrams are dominated by SM and loop diagrams could contain NP

      Tree diagram example Loop diagram example

    American Physical Society, Feb. 16, 2010


    Tree level only

    Tree Level Only

    • Tree diagrams are unlikely to be affected by physics beyond the Standard Model

    American Physical Society, Feb. 16, 2010


    Cp violation in b o k o only

    CP Violation in Bo & Ko Only

    • Absorptive (Imaginary) of mixing diagram should be sensitive to New Physics

    American Physical Society, Feb. 16, 2010


    They are consistent

    They are Consistent

    American Physical Society, Feb. 16, 2010


    Limits on new physics from b o mixing

    Limits on New Physics From Bo Mixing

    • Is there NP in Bo-Bo mixing?

    • Assume NP in tree decays is negligible, so no NP in |Vij|, g from B-DoK-.

    • Allow NP in m, weak phases, ASL, & G.

    95% c. l.

    • Room for new physics, in fact

    • SM is only at 5% c.l.

    American Physical Society, Feb. 16, 2010


    Limits on new physics from b s mixing

    Limits on New Physics From BS Mixing

    • Similarly for BS

      • One CP Violation measurement using BSJ/ 

    • Here again SM is only at 5% c.l.

    • Much more room for NP due to less precise measurements

    American Physical Society, Feb. 16, 2010


    New physics models

    New Physics Models

    • There is, in fact, still lots of room for “generic” NP

    • What do specific models predict?

      • Supersymmetry: many, many different models

      • Extra Dimensions: 

      • Little Higgs: 

      • Left-Right symmetric models 

      • 4th Generation models 

    • NP must affect every process; the amount tells us what the NP is (“DNA footprint”)

    • Lets go through some examples, many other interesting cases exist

    American Physical Society, Feb. 16, 2010


    Supersymmetry mssm

    Supersymmetry: MSSM

    • Contributions to direct CP violating decay

    B-fK-

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

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

    • Contributions to Bs mixing

    BsJ/yfoor f

    measures

    CP violating

     -2s

    fo, f

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

    American Physical Society, Feb. 16, 2010


    Supersymmetry su 5 u 2

    Supersymmetry: SU(5) &U(2)

    • -2bScan deviate from the “SM” value of -0.036 in SU(5) GUT non-degenerate case, and the U(2) model. From Okada’s talk at BNMII, Nara Women’s Univ. Dec., 2006

    SU(5) GUT

    Degenerate

    SU(5) GUT

    Non-degenerate

    U(2) FS

    -2bS

    American Physical Society, Feb. 16, 2010


    Extra dimensions

    Extra Dimensions

    • Using ACD model of 1 universal extra dimension, a MFV model, Colangelo et al predict a shift in the zero of the forward-backward asymmetry in B→K*m+m-

    • Insensitive to choice of form-factors. Can SM calculations improve?

    SM prediction form-factor 2

    SM prediction form-factor 1

    AFB

    American Physical Society, Feb. 16, 2010


    The lhcb detector

    The LHCb Detector

    American Physical Society, Feb. 16, 2010


    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’s

    American Physical Society, Feb. 16, 2010


    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

    American Physical Society, Feb. 16, 2010


    The forward direction at the lhc

    The Forward Direction at the LHC

    Pythia production cross section(14TeV)

    100 mb

    230 mb

    • 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)

    American Physical Society, Feb. 16, 2010

    21


    The lhcb detector1

    The LHCb Detector

    American Physical Society, Feb. 16, 2010


    The status of lhcb

    Detector Workings

    LHCb detector ~ fully installed and commissioned  walk through the detector using the example of a Bs→DsK decay

    American Physical Society, Feb. 16, 2010


    B vertex measurement

    B-VertexMeasurement

    144 mm

    47 mm

    K

    K

    Bs

    K

    Ds

    

    d~1cm

    440 mm

    Example: Bs → Ds K

    s(t) ~40 fs

    f

    sensors

    R

    sensors

    Primary vertex

    Decay time resolution = 40 fs

    Vertex Locator (Velo)

    Silicon strip detector with

    ~ 5 mm hit resolution

     30 mm IP resolution

    • Vertexing:

    • trigger on impact parameter

    • measurement of decay distance (time)

    American Physical Society, Feb. 16, 2010


    Momentum and mass measurement

    Momentum and Mass measurement

    p+, K

    Bs

    K

    K

    Ds

    

    Primary vertex

    btag

    Momentum meas. + direction (VELO): Mass resolution for background suppression

    Mass resolution

    s ~14 MeV

    Bs→ Ds K

    Bs →Ds p

    American Physical Society, Feb. 16, 2010


    Hadron identification

    Hadron Identification

    RICH: K/p identification using Cherenkov light emission angle

    Bs → Ds K

    SS flavour tagging

    ,K

    Bs

    KK : 96.77 ± 0.06%

    pK : 3.94 ± 0.02%

    K

    K

    Ds

    

    Primary vertex

    btag

    • RICH1: 5 cm aerogel n=1.03

      • 4 m3 C4F10 n=1.0014

    RICH2: 100 m3 CF4 n=1.0005

    American Physical Society, Feb. 16, 2010


    Particle identification and l0 trigger

    Particle identification and L0 trigger

    K

    Bs

    K

    Ds

    K

    

    btag

    Primary vertex

    e

    h

    ECAL (inner modules): σ(E)/E ~ 8.2% /√E + 0.9%

    • Calorimeter system :

    • Identify electrons, hadrons, π0 ,γ

    • Level 0 trigger: high ET electron and hadron

    American Physical Society, Feb. 16, 2010


    Particle identification and l0 trigger1

    Particle identification and L0 trigger

    K

    Bs

    K

    Ds

    K

    

    btag

    Primary vertex

    m

    • Muon system:

    • Level 0 trigger: High Pt muons

    • OS flavour tagging

    American Physical Society, Feb. 16, 2010


    The status of lhcb

    Triggering

    Trigger is crucial as σbb is less than 1% of total

    inelastic cross section and B decays of

    interest typically have B< 10-5

    40 MHz

    L0

    m

    L0

    had

    L0

    e, g

    Level -0

    • Hardware level (L0)

      Search for high-pT μ, e, γ and hadron candidates

    • Software level (High Level Trigger, HLT)

      Farm with O(2000) multi-core processors

      HLT1:Confirm L0 candidate with more complete

      info, add impact parameter and lifetime cuts

      HLT2: B reconstruction + selections

    1 MHz

    ECAL

    Alley

    Had.

    Alley

    Muon

    Alley

    HLT1

    High-Level Trigger

    30 kHz

    Global reconstruction

    Inclusive selections

    m, m+track, mm, topological, charm, ϕ

    HLT2

    & Exclusive selections

    2 kHz

    Storage: Event size ~35kB

    American Physical Society, Feb. 16, 2010


    Commissioning

    Commissioning

    American Physical Society, Feb. 16, 2010


    Commissioning with cosmics

    Commissioning with Cosmics

    • Challenge: LHCbis NOT suited for cosmics

      • “Horizontal” cosmics well below a Hz

      • Still 1.6x106good events (July – September 2008 ) recorded for Calorimeters

        & Muon

    • Alignment in time and space was done

    • L0 trigger parameters were set

    American Physical Society, Feb. 16, 2010


    A first glimpse of lhc protons

    A First Glimpse of LHC Protons

    • .

    [email protected] Sector Tests

    • Beam 2 dumped on injection line beam stopper (TED)

      • 4 m tungsten, copper, aluminium, graphite rod in a 1m diameter iron casing

      • 340 m before LHCb along beam 2

      • “Wrong” direction for LHCb

      • Centre of shower in upper right quadrant

      • High flux, centre of shower O(10) particles/cm2

      • Vertex Locator O(0.1) particles/cm2

    TI8

    TED

    LHC

    American Physical Society, Feb. 16, 2010


    A first glimpse of lhc protons1

    A First Glimpse of LHC Protons

    Scintillator Pad Detector

    Vertex Locator

    Muon : 70 candidates in average per shot

    Velo tracks, August 22, 2008

    American Physical Society, Feb. 16, 2010


    Velo space alignment with ted

    The detector displacement from metrology usually is less than 10 m

    Module alignment precision is about 3.4 m for X and Y translation and 200 rad for Z rotation

    VELO Space Alignment with TED

    R residuals

     residuals

    American Physical Society, Feb. 16, 2010


    Lhcb data

    LHCb Data

    • A few glimpses of real pp collision data (0.9 TeV)

    VELO partially closed

    American Physical Society, Feb. 16, 2010


    More lhcb data

    More LHCb Data

    American Physical Society, Feb. 16, 2010


    Some interesting measurements sensitivities

    Some Interesting Measurements & Sensitivities

    LHCb expectations:  300 fb-1 in 2010

    ~ 2 fb-1 for nominal yr

    ~ 10 fb-1 for “1st run”

    ~100 fb-1 for upgrade

    American Physical Society, Feb. 16, 2010


    General strategy

    General Strategy

    • Measure experimental observables sensitive to New Particles through their interference effects in processes mediated by loop diagrams, e.g.

      • CP violation via mixing

      • Example

    q

    b

    u,c,t

    W−

    W+

    q

    u, c, t

    b

    American Physical Society, Feb. 16, 2010

    Viq

    V*ib


    Cp asymmetry in b s j f

    CP Asymmetry in BSJ/ f

    • Just as BoJ/ KS measuresCPV phase 2bBSJ/ f measures CPV BS mixing phase -2bS

    • Since this is a Vector-Vector

      final state, must do an angular

      (transversity) analysis

    • The width difference DGS/GS

      also enters in the fit

    • Combined current CDF & D0

      results

    • LHCb will get 131,000 such

      events in 2 fb-1. Projected errors are ±0.03 rad in 2bS & ±0.013 in

      DGS/GS. [Will also use J/ fo(980)]

    1sLHCb in 2 fb-1

    American Physical Society, Feb. 16, 2010


    B s right handed currents

    BS: Right-Handed currents

    • Define , zero in SM

    • Theory

      where AD=sin2y

    • Sensitivity (assume DGS/GS=0.12)

    • s(sin2y)=0.22 2fb-1

    • s(sin2y)=0.10 10fb-1

    • s(sin2y)=0.02 100fb-1

    AD=0.4

    AD=0

    American Physical Society, Feb. 16, 2010


    B s m m supersymmetry

    BS→m+m- & Supersymmetry

    • Branching Ratio very sensitive to SUSY

    • In MSSM goes as tan6b

    SM

    Gaugino mass

    American Physical Society, Feb. 16, 2010


    B s m m

    BS→m+m-

    • With 10 fb-1 barely able to make significant SM level measurement

    • Precision measurement requires 100 fb-1

    CDF+D0 expected

    9 fb-1

    5s measurement

    3s measurement

    American Physical Society, Feb. 16, 2010


    B k m m

    BK*m+m-

    • Standard Model:

    • Supersymmetry:

    American Physical Society, Feb. 16, 2010


    The status of lhcb

    B→K*

    • Described by three angles (ql, f, qK) and di-m invariant mass q2

    • Forward-backward asymmetry AFBof qldistribution of particular interest:

      • Varies between different NP models →

      • At AFB = 0, the dominant theoretical uncertainty.fromBd→K*form-factors cancels at LO

    American Physical Society, Feb. 16, 2010


    The status of lhcb

    B→K*+-

    • State-of-the art is recent 625 fb-1 Belle analysis ~ 250 K* arXiv:0904.07701

    • CDF have ~20 events

      in 1 fb-1arXiv:0804.3908

    • LHCb expects ~750 in 300 pb-1(with +- only)

    • ~7k events / 2fb-1 with B/S ~ 0.2. After 10 fb-1zero of AFB located to ±0.28 GeV2

    American Physical Society, Feb. 16, 2010


    Other angular variables in k m m

    Other Angular Variables in K*m+m-

    • Supersymmetry(Egede, et al... arXiv:0807.2589)

    • Use functions of the transverse polarization

    i are form factors

    10 fb-1

    model 1

    With more L can distinguish between

    different SUSY models in some cases

    American Physical Society, Feb. 16, 2010


    Exotic searches

    Exotic Searches

    • LHCb complements the ATLAS/CMS solid angle by concentrating at large h and low pt

    • Sensitive to “Exotic” particles decaying into lepton or quark jets, especially with lifetimes in the range of 500>t>1 ps.

    • We will show one example, that of “Hidden Valley” Higgs decay

    American Physical Society, Feb. 16, 2010


    Search for hidden valleys

    Search for Hidden Valleys

    • New heavy Gauge sectors can augment the Standard Model (SM) as well SUSY etc..

    • These sectors arise naturally in String theory

    • It takes Energy to excite them

    • They couple to SM via Z′ or heavy particle loops

    • From Strassler & Zurek [hep-ph/604261]

    American Physical Society, Feb. 16, 2010


    Search for exotic higgs decays

    Search for Exotic Higgs Decays

    • Recall tension between predicted SM Higgs mass using Electroweak data & direct LEP limit

    • Limit is based on SM decays, would be void if there were other modes

    • Hidden Valley provides new scalars pov, allowing Ho povpov bb, with long lifetimes possible.

    American Physical Society, Feb. 16, 2010


    Mass resolutions

    Mass Resolutions

    • Expect a few thousand reconstructed decays in 2 fb-1

    American Physical Society, Feb. 16, 2010


    The lhcb upgrade

    The LHCb Upgrade

    American Physical Society, Feb. 16, 2010


    How we can upgrade

    How We Can Upgrade

    • Run at higher luminosity

    • Improve efficiencies

      • especially for hadron trigger

      • Photon detection

      • Tracking, e.g. reduce material

    • Improve resolutions

      • Photon detector

      • RICH

    • Basically build a better magnifying glass!

      • New VELO, etc…

    American Physical Society, Feb. 16, 2010


    Current trigger efficiency

    Current Trigger Efficiency

    L0 efficiency (%)

    • As usual define trigger e= # events accepted by trigger / # of events found after all other analysis cuts

    • L0 typically is 50% efficient on fully hadronic final states

    • HLT1 is 60% on DSK-

    • HLT2 is 85% on DSK-

    • Product is 25%, room for improvement

    American Physical Society, Feb. 16, 2010


    Our goal

    Our Goal

    • To collect signal at >10 times current rate, then we will possess the most powerful microscope known to man to probe certain physical processes

      • We will use specific channels and show rates can be increased, but the idea is to be able to increase data on a whole host of channels where new ones may become important

    • We are taking into account possible changes due to the LHC schedule…

    American Physical Society, Feb. 16, 2010


    Current running conditions

    Current Running Conditions

    • Luminosity 2x1032 cm-2/s at beginning of run

    • Take s = 60 mb, [s(total) - s(elastic) - s(diffractive)]

    • Account for only 29.5 MHz of two filled bunches

    • Most xings don’t have an interaction

    • Need 1st level trigger “L0” to reduce data by factor~30 to 1 MHz

    • Higher Level Triggers reduce output to 2 kHz

    Fraction

    American Physical Society, Feb. 16, 2010


    Upgrade running conditions

    Upgrade Running Conditions

    • First step run to 1033 increases average # of int/crossing to only ~2.3

    • Second step to2x1033 increases to ~4.6

    • Trigger change: will readout entire detector each crossing & use software to select up to 20 kHz of events

    Fraction

    American Physical Society, Feb. 16, 2010


    One ex lhcb sensitivities for 2 b s

    One Ex: LHCb Sensitivities for 2bS

    • With 100 fb-1 (LHCb upgrade) error in -2bS decreases to ±0.004 (only L improvement), useful to distinguish among Supersymmetry (or other) models (see Okada slide), where the differences are on the order of ~0.02

    American Physical Society, Feb. 16, 2010


    4 th generation model

    4th Generation Model

    • New heavy t quark

    • Changes many rates & CPV in many modes

    • Ex.

    • Soni et al arXiv:1002.0595

    • Likely to need 100 fb-1 to distinguish among models

    mt=600 GeV

    B(Bsm+m-)

    mt=400

    GeV

    SM Prediction

    2bs

    American Physical Society, Feb. 16, 2010


    Conclusions

    Conclusions

    • We hope to see the effects of new particles observed by ATLAS & CMS in “flavor” variables in 10 fb-1

    • Upgrading will allow us to precisely measure these effects

    American Physical Society, Feb. 16, 2010


    The future

    The Future

    • Yogi Berra: “Its difficult to make predictions, especially about the future”

    • Possibilities:

    • Fourth possibility too depressing to list, but LHCb measurements could set the scale of where we would have to go next

    American Physical Society, Feb. 16, 2010


    The end

    The End

    American Physical Society, Feb. 16, 2010


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