Early physics with the LHCb detectorlhcb-doc.web.cern.ch/.../dirk_wiedner_perugia_talk.pdf · 2008-06-25 · 27 June 2008 Dirk Wiedner at PIC2008 Perugia 1 Early physics with the

27 June 2008 Dirk Wiedner at PIC2008 Perugia 1

Early physics with the LHCb

detector

Dirk Wiedner

CERN

for the LHCb collaboration

XXVIII PHYSICS IN COLLISION - Perugia, Italy, June, 25-28, 2008


Outline

• LHCb detector

• First days of data taking

• Beauty cross section

• Summary and Outlook


LHCb @ LHC

A Large Hadron Collider Beauty Experiment for Precision Measurements of CP-Violation and Rare Decays

CMS ALICE

ATLAS

LHCbCERN

√s = 14 TeVLHCb: L=2-5 x 1032 cm-2 s-1

bb = 500 b

inel / bb = 160=> 1 “year” = 2 fb-1

b

b

b

b


Beryllium beam pipe

The LHCb Detector


Beryllium beam pipe

The LHCb Detector

VELO

Muon det Calo’s RICH-2 MagnetOT RICH-1


Beryllium beam pipe

The LHCb Detector

VELO

Muon det Calo’s RICH-2 MagnetOT RICH-1

VELO

Muon det Calo’s RICH-2 MagnetOT+IT RICH-1

Installation of major structures is complete


A walk through the LHCb spectrometer…


B-Vertex Measurement

Vertex Locator (Velo)

Silicon strip detector

8 mm from beam with

~ 5 m hit resolution

30 m IP resolution


B-Vertex Measurement

Vertex Locator (Velo)

Silicon strip detector

8 mm from beam with

~ 5 m hit resolution

30 m IP resolution

Vertexing:• Impact parameter trigger• Decay distance (time) measurement

Ds

Bs K

K

K

d≈1 cm

47 m 144 m

440 m

Primary vertex

Decay time resolution = 40 fs

) ~40 fs

Example: Bs → Ds K


Momentum and Mass measurement

Momentum meas.: Mass resolution for background suppression







Mass resolution~14 MeV

B mass resolution

15-20 MeV/c2

Bs μμ

Bs KK


Cherenkov rings RICH1

Particle Identification

RICH: K/ identification using Cherenkov light emission angle

RICH1: 5 cm aerogel n=1.03

4 m3 C4F10 n=1.0014 RICH2: 100 m3 CF4 n=1.0005


Cherenkov rings RICH1


RICH: K/ identification using Cherenkov light emission angle


4 m3 C4F10 n=1.0014 RICH2: 100 m3 CF4 n=1.0005



RICH2: 100 m3 CF4 n=1.0005

RICH: K/ identification; eg. distinguish Ds and DsK events.


4 m3 C4F10 n=1.0014

Cerenkov light emission angle

Bs → Ds K

btag

Bs K

K

,K

Ds

Primary vertex

KK : 97.29 ± 0.06%K : 5.15 ± 0.02%


LHCb calorimeters

e

h

Bs KK

K

Ds

Primary vertex

Calorimeter system : • Detection of electrons, π0, γ• Level 0 trigger: high ET electron and hadron, photon

btag


LHCb calorimeters

e

h

Bs KK

K

Ds

Primary vertex

btag

Calorimeter system : • Detection of electrons, π0, γ• Level 0 trigger: high ET electron and hadron, photon


LHCb muon detection

Muon system:• Level 0 trigger: High Pt muons•Muon ID


LHCb muon detection

Muon system:• Level 0 trigger: High Pt muons•Muon ID


LHCb trigger

HLT

rateEvent type Physics

200 Hz Exclusive B

candidates

B (core program)

600 Hz High mass di-

muons

J/ , b J/ X (unbiased)

300 Hz D* candidates Charm (mixing & CPV)

900 Hz Inclusive b (e.g.

b )

B (data mining)

HLT: L0 confirmation with improved detector resolution, followed by full event reconstruction

40 MHz

1 MHz

2 kHz

L0: high pT ( , e, , h) [hardware, 4 s]

Storage (event size ~ 50 kB)

DetectorL0, HLT and L0 HLT efficiency


Cosmic muon event

The detector is ready!


Initial minimum bias run• only 4 filled bunches at L = 1.1 x 1029cm-2s-1

• 2 kHz minimum bias to disk

• 300 Hz non-empty minimum bias events to disk

• 108 events in approx. 100 hours of running

Parameters Rates in 8

kb Nbeta* Luminosity Events/

(m) (cm-2

s-1

) crossing

68 4 1010

10 2.0E+30 0.15

68 4 1010

5 4.9E+30 0.3

68 9 1010

10 9.6E+30 0.76

68 9 1010

5 2.4E+31 1.6

Filling scheme for next step (2008)


1.E-10

1.E-09

1.E-08

1.E-07

1.E-06

1.E-05

1.E-04

1.E-03

1.E-02

1.E-01

1.E+00

1.E+01

1.E+00 1.E+02 1.E+04 1.E+06 1.E+08 1.E+10 1.E+12 1.E+14

σε/σmb

Nmb

π± production

Bd→J/ΨKs production

J/Ψ production D-meson production

Λbar production

K0 production

φ production

Λ production

π0 production

J/Ψ from bb

Physics reach vs integrated

luminosity

108 minimum bias @ 2kHz


Beauty x-section

• Requirement: working MUON-system,

Main Tracker and VeLo

• measure J/Ψ -production cross

sections

• disentangle fractions of prompt and

detached J/Ψs

• relate non promt J/Ψ yield to bb cross

sections


Summary

• The LHCb detector is ready to take data in

2008:– Good decay time resolution to resolve Bs oscillations

– Good mass resolution to efficiently suppress background

– Excellent particle identification for K-π separation

– Efficient trigger for many B-decay topologies

• Inclusive “low pT” physics from day one

• Determination of the b-cross section in first

months


Outlook• Physics program in 2009:

– Very interesting results with first 0.5 fb-1 of data: Bs J/ s measurement with 0.05 precision (S.M. exp. 0.0368 0.0017)

Bs BR limit down to SM value (3.35 0.32) x10-9

Bd K0* 1800 events, overtaking B-Factories statistics

• Core physics program @ 2fb-1 per year

CP Violation - 1 year (2 fb-1)

• from trees: 5o - 10o

• from penguins: 10o

• Bs mixing phase: 0.023

• seff from penguins: 0.11

Rare Decays - 1 year (2 fb-1)

• BdK0* s0 : 0.5 GeV2

• Bsφ Adir , Amix : 0.11

A : 0.22

• Bs BR.: 6 x 10-9 at 5If N.P.!


The End


√s = 7 TeVLHCb: L=2-5 x 1032 cm-2 s-1

bb = 500 b

inel / bb = 160=> 1 “year” = 2 fb-1

A Large Hadron Collider Beauty Experiment for Precision Measurements of CP-Violation and Rare Decays

CMS

ALICE

ATLAS

LHCb

CERN


LHCb detectorRICH: PID

K, separationCalorimeter:

PID: e, , 0

Muon System

Vertex Locator:

• primary + secondary

vertex

• impact parameter

Trigger Tracker:

pt for Trigger

Tracking Stations:

pt of charged particles

Particle ID:

Tracking:


Luminosity (1/4)

Massimiliano FERRO-LUZZI


Luminosity (2/4)• Beam shape and position

measurement

• Use beam-gas interaction

vertices

– Vertex locator

• resolution 30 µm in x and y,

depending on # of tracks

– 10-7 mbar Xenon or other

noble gas

– 30 Hz beam-gas collision rate


Luminosity (3/4)– Bunch profile mapping within

minutes O(1%)

– Normalize beam-beam x-

section on beam-gas x-

section

• Absolute luminosity during

physics run feasible

– …but calibration run

advisable or

– L0 trigger on activity for any z

--- beam1-gas … beam2-gas

__ beam1-beam2 __ sum

ALL from:

Massimiliano FERRO-LUZZI

-1 10 [m]


Efficiency = 91%Purity = 97±3%

180 events per pb-1

5 pb-1 3 % statistical error.

Total L error ≤ 5%

if data understood

Z→μ+μ- events

Tara Shears


PDF @ LHCb• Unique phase space

covered by LHCb

• Z and W differential cross-

section from

– Z →µ+µ-, W→µν

• 10pb-1 enough for

improvement on PDF

uncertainties, today up to

50%

Z0→µ+µ-

Documents

Early physics with the LHCb detectorlhcb-doc.web.cern.ch/.../dirk_wiedner_perugia_talk.pdf · 2008-06-25 · 27 June 2008 Dirk Wiedner at PIC2008 Perugia 1 Early physics with the