Performance of the LHCb calorimeters · Y~7m X~8.5m Z~2.7m PS/SPD LHCb Calorimeters 20131125 V CPAN...

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Performance of the LHCb calorimeters during the period 2010-2012 Xavier Vilasís-Cardona 20131125 V CPAN Days - Xvc 1

Transcript of Performance of the LHCb calorimeters · Y~7m X~8.5m Z~2.7m PS/SPD LHCb Calorimeters 20131125 V CPAN...

Page 1: Performance of the LHCb calorimeters · Y~7m X~8.5m Z~2.7m PS/SPD LHCb Calorimeters 20131125 V CPAN Days - Xvc 2 10#250&mrad 10#300&mrad VELO Vertexing MAGNET Calorimeters PID: e,γ,

Performance of the LHCb calorimeters during the period 2010-2012

Xavier Vilasís-Cardona

20131125 V CPAN Days - Xvc 1

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Y~7m X~8.5m

Z~2.7m

HC

AL

ECA

L

PS/SPD

LHCb Calorimeters

20131125 V CPAN Days - Xvc 2

10-­‐250  mrad

10-­‐300  mrad

VELO Vertexing

MAGNET

Calorimeters PID: e,γ, π0

Muon Stations

RICH 1 & 2 PID: K vs. π

Trackers TT+IT+OT Momentum resolution

•  Preshower (PS)/Scintillator Pad Detector (SPD)

•  Electromagnetic Calorimeter (ECAL) •  Hadronic Calorimeter (HCAL)

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Purpose of LHCb calorimeters

•  Preshower (PS) and Scintillator Pad Detector (SPD): •  PID for L0 electron and photon trigger •  electron, photon/pion separation by PS •  photon/MIP separation by SPD •  charged multiplicity veto by SPD

•  Electromagnetic Calorimeter (ECAL): •  Et of electrons, photons and π0 for L0 trigger (e.g. B → J/Ψ Ks,

B → K*γ) •  reconstruction of π0 and prompt γ offline •  particle ID

•  Hadron Calorimeter (HCAL): •  Et of hadrons for L0 trigger (e.g. B → π π , B → DsK) •  particle ID

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PS and SPD

•  Scintillator blocs with coiled WLS fiber •  Geometry projective with ECAL: 3 zones •  MAPMT Hamamatsu 5900 M64 •  6016+6016 Cells

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Side view of upper part

Inner + Middle + Outer Modules

e-

γ

SPD Pb PS ECAL

JINST 3 S08005 (2008)

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ECAL

•  Shashlik •  PMT readout Hamamatsu R7899-20

•  Energy resolution σ(E)/E = 0.085 ± 0.01/ E ⊕ 0.008 ⊕ 0.003 ∗ x/E

•  6016 cells

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3312 shashlik modules with 25 X0 Pb Inner

Module 9 cells: 4x4 mm2

Middle Module 4 cells: 6x6 mm2

Outer Module 1 cell: 12x12 mm2

Sc:Pb = 4:2 mm 25 X0

12x12 mm2

Chariot

Electronic platform

modules

Beam plug JINST 3 S08005 (2008)

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HCAL

•  Tile structure •  PMT readout Hamamatsu R7899-20 •  Energy resolution √σ(E)/E = (0.69 ± 0.05)/ E ⊕ (0.09 ± 0.02) •  1488 Cells (inner-outer)

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particles

PMT

scintillators

WLS fibers light-guide

Electronics platform

Chariot

modules

Beam plug

Weight : ~9.5 ton

JINST 3 S08005 (2008)

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Front End Electronics

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Installation and Commissioning

•  Installation from 2004-2008 •  Commissioning 2005-2009 •  First cosmic seen January 2008 •  Commissioning using built in

monitoring tools, cosmics and splash events.

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OT

Calo Muon

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Calibration and Monitoring

•  Calibration strategies – PS / SPD

•  Fit the MIP signal and look for efficiencies

– ECAL •  Initial adjustment •  Energy Flow

•  Fit π0 mass •  E/p for electrons

– HCAL •  Built in 137Cs source

•  Detectors include built in LED system for monitoring detector stability

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LED monitoring system of XCAL

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LED LED LED LED LED LED LED

Driver Splitter

PIN diode ADC

LED LED LED LED LED PMT …

•  Control of time and temperature stability •  Small pulse duration and dispersion of amplitude •  Adjustable pulse rate and amount of light •  Emulate e/m particles in full “physics” region •  Gain control to better than 1% accuracy •  Control only electronics chainà supply LED light directly to the

PMT •  Use empty bunches for running monitoring system

ECAL Ø  512 LED drivers & LEDs

& splitters & fiber-bundles

Ø  64 PIN-diodes

LED pulse

50 GeV e-

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PS-SPD

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•  Tracks pointing to given PS/SPD cell are extrapolated •  PS: MIP signal is fitted and fixed to a given number

of ADC counts •  SPD: signal is checked for existing tracks

Mean 0.9487RMS 0.03373

Cell efficiency0.6 0.65 0.7 0.75 0.8 0.85 0.9 0.95 10

10

20

30

40

50

Mean 0.9487RMS 0.03373

Even BXApril2011MPV0 2 4 6 8 10 12 14 16 18 20

Cha

nnel

s

0

20

40

60

80

100

120

140

160

180 Even BX A sideApril2011MPV

Outer \bar{x}: 7.79 \pm 0.03 \sigma: 1.20 \pm

Middle \bar{x}: 7.52 \pm 0.04 \sigma: 1.17 \p

Inner \bar{x}: 7.88 \pm 0.05 \sigma: 1.27 \pm

SPD Efficiencies (2011) PS MIP Energy Distribution April 2011

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HV, kV

G

0.6 0.8 1.21.0 1.4

104

105

ECAL – Initial calibration + Energy Flow

•  Initial Calibration (relative width of π0 peak, 10%)

•  Energy Flow –  Equalize the energy flow over 3x3 cell blocks

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Entries 6016

Mean 0.009065

RMS 0.03534

−0.5 −0.4 −0.3 −0.2 −0.1 0 0.1 0.2 0.3 0.4 0.50

100

200

300

400

500

600

700Entries 6016

Mean 0.009065

RMS 0.03534

MiscalibrationCalibrationResiduals

10% miscalibration

ADCmax

= Emax

e kY G

nominal

sADC

MC data

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ECAL – Fine Calibration

•  Currently absolute calibration based on the ‘Mass distribution fit’ method

(O.Igonkina et al. HERA-B 00-103)

•  Fit π0 mass from 2 photon signals in ECAL •  Iterative procedure

–  Select photons (3x3 clusters) and fix seed (central) cell. –  For each cell –  Compute di-photon invariant mass –  Fit π0 mass distribution –  Correct calibration of seed cells –  Restart until stable

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π0 mass

ConclusionsThe Mass distribution fit method was applied as the final step of the calibration for 2011 data.With the set of data corresponding to one week of data taking 6015 coefficients for 6016 cells wereobtained. One more cell gave too low signal due to the faulty electronics, so no coefficient could befound for it.

In Fig.4 one may see the γγ invariant mass distribution before (blue line) and after (red line)the calibration. With the help of calibration the neutral pion peak position has moved to its nominalvalue and its resolution became smaller by 12%. Several more evidences of the performanceimprovement may be found in the Appendix.

Mass 0.0± 135.3

Width 0.007± 7.568

0 50 100 150 200 2500

500

1000

1500

2000

2500

310×

Mass 0.0± 135.3

Width 0.007± 7.568

Mass 0.0± 131.7

Width 0.010± 8.559

Mass 0.0± 131.7

Width 0.010± 8.559

Mass 0.0± 131.7

Width 0.010± 8.559

dN

dM

π0

!

1M

eV/c

2

"

Mass (MeV/c2)

Figure 4: γγ invariant mass distribution before (blue line) and after (red line) calibration.

AcknowledgmentsWewould like to say many thanks to the calorimeter calibration group for lots of fruitful discussions,to Dr. M.-N.Minard, Dr. P.Perret, Dr. J.Lefrancois and A.Martens for their kind help and A.PuigNavarro for his invaluable impact to this job.

8

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Mass distribution fit algorithm 2011 data (june)

Initial calibration value

Final calibration value About 6% error

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E/p

•  Another method to monitor or correct the ECAL cell calibration is through electron E/p

•  Electrons are identified by estimation of the momentum of the extrapolated of tracks and energy of the matching clusters.

•  Used to monitor ageing.

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0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 20

0.02

0.04

0.06

0.08

0.1

0.12

0.14

0.16 E/p for electrons in ECAL E/p for hadrons in ECAL 2011 data

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Ageing on ECAL –  π0 mass variation as a function of time (luminosity) observed:

V CPAN Days - Xvc 20131125

–  Optical fibres of ECAL LED monitoring system are also affected –  The effect is cured by calibrating ECAL:

•  Apply fine calibration of each ECAL cell using π0 and adjusting its mass on a short period of data taking

•  On top of fine-calibrated data trending coefficients are applied: –  π0 statistic not high enough to follow closely the changes –  Make use of photon conversion and look at E/p

Run Number115 120 125 130

310×

Pi0

mas

s pe

ak (M

eV/c

2)

130131132133134135136137138139140

p0 0.01735± 135.1 p0 0.01735± 135.1

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HCAL Calibration •  HCAL absolute Calibration

–  Based on 137Cs source scans performed during technical stops

–  LEDs used to monitor.

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The “PMT sensitivity variation” is the PMT gain variation reduced to the initial (March 2011) HV, calculated from the calibration coefficients.

Ageing on HCAL (both on detector and PMT)

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Can be corrected by Modifying PMT gain (HV) Calibration

Cs source runs + LED Scintillator rows in the tile get affected depending on their depth

20131125

PMT gain Loss expected With cumulated charge

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Photon Reconstruction

•  Clusters : 3x3 cells –  Barycenter, –  Energy –  Spread

•  Match fitted tracks to discard charged particles

•  Mass resolution :

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B0d ! K0⇤� L = 1.0fb�1

Ec = ↵"cl + �"PS

100MeV/c2

�22D(~p) =

(~ptr � ~p)T C�1tr (~ptr � ~p)

+ (~pcl � ~p)TS�1cl (~pcl � ~p)

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π0 reconstruction

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•  Neutral π0 –  Low energy : resolved pair of γ – mass resolution : 8 MeV/c2

–  High energy (pT>2GeV/c): overlapped γ clusters – iterative algorithm to separate in two subclusters – mass resolution : 20 MeV/c2

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0.45 0.5 0.55 0.6 0.65 0.7 0.750

0.2

0.4

0.6

0.8

1

ρ vs ∈

SPDρ vs ee→ γ∈

SPDρ vs ee→ γ∈

0.45 0.5 0.55 0.6 0.65 0.7 0.75 0.8 0.850

0.2

0.4

0.6

0.8

1

ρ vs ∈

SPDρ vs ee→ γ∈

SPDρ vs ee→ γ∈

Photon identification and merged π0 •  Photon Hypothesis uses

–  PS cells in front of ECAL cells energy, Ratio of energy (central cell/cluster), Χ2

2D

•  Separating merged π0 from γ –  Uses cluster shape –  MLP –  Trained on simulation –  Checked on data B and D decays

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pT>500MeV/c

pT>200MeV/c

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Converted Photon Reconstruction

•  Converted photons produce a pair (ee) •  Correct for e bremsstrahlung

–  Bremsstrahlung candidate : neutral energy deposition with Χ2 < 300 from a charged track.

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h1Entries 10

Mean 1404RMS 522.6

(MeV/c)γTP

600 800 1000 1200 1400 1600 1800 2000 2200 2400

)C

ALO

γ(∈)/eeγ(∈

0

0.005

0.01

0.015

0.02

0.025

0.03

0.035

0.04

0.045

0.05h1

Entries 10

Mean 1404RMS 522.6

h60Entries 138690Mean 135.5RMS 31.19

60 80 100 120 140 160 180 200

500

1000

1500

2000

2500

3000

3500

4000

h60Entries 138690Mean 135.5RMS 31.19

h40Entries 6353Mean 137.4RMS 33.04

h40Entries 6353Mean 137.4RMS 33.04

⇡0 ! �(! ee)�CALO

Data MC

✏(� ! ee)/✏(�CALO)

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Electron Identification

•  Build reference histograms –  use converted γ reconstructed from events triggered

by muon detector –  Hadron background made of π and K from D0

decays –  Use 340 pb-1 from 2011 data

•  Histograms built for PS, ECAL and HCAL •  Identification is based on E/p refined using

X22D and also EPS and EHCAL

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EPS

E/p

EHCAL Χ22D

LCALOeh = LECAL

eh LHCALeh LPS

eh

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Combined Performance of electron identification

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� logLCALOeh > 0

� logLCALOeh > 1

� logLCALOeh > 2

� logLCALOeh > 3

Electron Efficiency

MisId rate

p

e h

Tag and probe method using e from

logLCALOeh

Probe e efficiency

B± ! J/ (e+e�)K±

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25

LHCb Upgrade Architecture

24th April 2013

CHEF 2013

Ken Wyllie, CERN 25

HLT

Current

HLT++ Upgrade

1MHz event rate

40MHz event rate

Readout Supervisor

L0 Hardware Trigger

Readout Supervisor

Low-Level Trigger

50 Tb/s

Low-Level Trigger

1 to 40 MHz

LOW Level Trigger decision

from Front-End to Back-End

20130521 Xvc - ISCAS 2013 25

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Upgrade

•  Increased luminosity •  New features •  PS and SPD shall be eliminated (they mainly

contribute to L0 trigger) •  DAQ @ 40MHz

–  Change in the readout electronics •  Lower PMT gain

–  Higher luminosity –  Ageing

•  New electronics under development •  TDR under review

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Conclusions

•  LHCb calorimeters fully functional •  Ageing observed

–  Frequent calibrations

•  Good performances in γ and e identification. •  Upgrade

–  Leave ECAL-HCAL –  Software trigger –  New DAQ electronics

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Performance of the LHCb calorimeters during the period 2010-2012

Xavier Vilasís-Cardona

20131125 V CPAN Days - Xvc 28

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BACKUP

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Time Alignment

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•  DAQ feature: Time Alignment Events •  Equalise an a-priori delay from theoretical values •  Adjust BXID so that an event is mainly seen on Current •  Adjust integration time t0

–  Select the pair of BX with maximum signal •  Prev1/Current vs. Current/Next1

–  Compute the asymetry R

•  All XCAL channels adjust within 1ns ∑∑

∑∑

+

−= Nevt

iij

Nevt

iij

Nevt

iij

Nevt

iij

NextECurrentE

NextECurrentERj

)()(

)()(

t T0 Next1 Prev1

25 ns

δTsampling δTsampling δTsampling

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First π0 fit – Nov 2009

•  Initial calibration was performed by setting a uniform ADC count value per transverse energy unit.

•  This calibration allowed to fit the π0 peak in NOV2009

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M=133 ± 3 MeV/c2, with σ = 11 ± 4

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B production in LHCb Ø  b and b quarks are produced in pairs Ø  bb production is correlated and sharply peaked forward-backward Ø  LHCb single-arm forward spectrometer : θ~15-300 mrad (rapidity range: 4.9>η>1.9) Ø  Cross section of bb production in LHCb acceptance: σbb ~ 230 µb Ø  LHCb limits luminosity to few 1032cm-2s-1 instead of 1034cm-2s-1

by not focusing the beam as much as ATLAS and CMS Ø  Maximizes probability of a single interaction per crossing Ø  Design luminosity from start-up of LHC Ø  ~ 1012 bb pairs produced/year in LHCb acceptance

pp interactions/crossing

LHCb

n=0

n=1

ATLAS/CM

S

boost

b

b

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LED monitoring system of HCAL

20131125 V CPAN Days - Xvc 33

Ø  blue LEDs (WU-14-750BC) Ø  two independent LEDs per module Ø  adjustable LED pulse amplitude Ø  monitoring PIN photodiode at each

LED in order to account for LED instability

Ø  light distribution with clear fibers of same length

Ø  timing of the LED flashing pulse adjustable with 1 ns step

0.2%

Monitoring of LED with PIN diode

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Radiative decays b→qγ

•  Radiative b→(d, s)γ, one-loop penguin transition, sensitive to NP.

•  Theoretically clean FCNC transition & experimentally accessible.

•  Many observables: branching fractions (BR), CP asymmetries (ACP), isospin asymmetry, helicity structure of the photon.

34

NP may introduce sizeable effects on the dynamics of the transitions, through contributions of new particles inside the loops

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Time Alignment results-ECAL

•  All XCAL channels adjusted within 1 ns.

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HCAL E/p offline calibration

V CPAN Days - Xvc 36

If the offline accounting for the HCAL ageing will be found necessary, one can use the E/p based calibration on hadron tracks (for the moment, available per fill, up to fill #2007, Aug-2011).

The E/p calibration gives absolute scale and calibrates the whole signal chain, accounting also for the spread of FEB sensitivities.

Here: correlation of ratio of E/p-based calibration coefficients for fill ranges 1883-1901 and 1997-2007 (~5 weeks in between) and LED amplitude change for the same period. This validates the use of the LED corrections at least for short time scale.

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