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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
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 VubLimits 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

slide23
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

slide29
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

slide44
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

slide45
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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