A new paper on muon detector performance-------

Discuss the paper content (bepo + roberta)

Martellotti 24-09-2010

Paper content (1)

LHCb muon detector calibration and performance (after HV optimization) with collisions tracks (field on – high p muons) Do not treat in detail MuonID and TRIGGER

Detector setting up - optimization of the chambers working point - time alignment

Detector performance - space alignment- cluster size - efficiency of the detector

Content (2)Same as in previous slide with an “Historical approach” (this approach could be used in the introduction to explain the work)

# A first setting up of the detector was performed in 2009 with hardware and software tools and the use of cosmic rays (ref). The settings chosen allowed to reach an adequate performance of the detectors to run the system with the first collisions with a reasonably good efficiency.# here we briefly report on the status of the detector at the time of very first collisions# we describe the subsequent improvements in the detector settings (noise, thr, HV,…) discussing the effects (…time shift…)# we describe the actions taken and procedures to improve the detector performance (new time alignment…)# we assess the “final” performance of the system with high momentum muons from collisions

Let’s go through possible CHAPTERS

to help discussion on- paper content - results already established- work to be done

The LHCb muon system

A full description of detector is needed once again ?

Probably yes. In the cosmic paper we started with a very short description and we were obliged to extend…

Track reconstruction & Data sample

# Are the track reconstruction algorithms different for different analysis ? Is it relevant ?# Data sample needed for analysis to be completed may be different for different analysis: - space alignment : new analysis needed. There is an “old stripping” of min. bias with “loose” muons that should be OK.- time alignment : data already analyzed. Old HV data for equalization inside regions + new HV - TAE mode (scanning). Do we need new analysis / new data sample for the paper? - cluster size : new analysis needed with single BC new HV data. Statistics needed?- efficiency : we need a new high statistics sample (new HV):Do we use downscaled minimum bias or make a selection of “non triggering” muons in triggered events ? Decision / Preparation of high statistics sample

Setting up of the detector1)Status of the detector settings and performance

at the beginning of LHC operation

- Briefly report on the hardware and software work done in 2009 to set up the detector for the first collisions (ref cosmic paper)

- recall the initial status of settings (and initial performance)

Do we report on the efficiency measured with the first 2009 collisions ???

(if not, I would unify this paragraph with the next one)

Setting up of the detector2) Optimization of the chambers working point

- principles - method - setting chosen : noise level, threshold, optimized HV. Explain the effects of changing settings (HV) on detector performance (time resolution and time alignment, cluster size, efficiency)

Are there other significant detector improvements to mention (dead channels recovered, actions taken for GEM, …) ?

Setting up of the detector3) New time alignment

# 1) equalization among channels of the same region Collision data with old HV have been used (much higher statistics available w.r.t. cosmics in the inner regions) # 2) optimization of the time offset per region with new HV (time-scanning data in TAE mode)

- shall we give chamber time resolution ? (problem with the distribution tails. I would avoid discussing again TDC) explain the “timing efficiency” in 25ns measured with TAE events as a direct consequence of the time resolution. - report about checks done, M1, dead channels …other items?- Is further analysis needed for the paper ? On which data ?(check with muons matched to high momentum tracks ?)

Detector performance 1) Space alignment

- alignment done with trigger unbiased muons (from min bias events) matched to high momentum tracks - We should conclude if hardware alignment is satisfactory (yes it is) and if further (minor) improvement is possible and useful. It would be good to have an (even rough) estimate of the effect of misalignment on Trigger efficiency.

# Global alignment with OT must be done. The “old” muon data sample from min bias is OK but probably we must re-run the events (tracking software modified) (*)# Alignment with MUON stand alone if possible should also be done (it is a complementary check…) (*) The present OT alignment should be good enough for us (Select field on – high momentum tracks) ?

Detector performance 2) Cluster size

Give CS along X (or X,Y separately). Report the CS for 5 stations 4 regions (average value and CS vs angle) Use events of single BC with final HV settings Select hits associated to high momentum tracks (for other selections see Walter – ambiguities, chamber edges….)Data sample ? Statistics needed ?

Explain the expected contribution from geometry… Explain the relevance of CS :show dependence on HV, stress the importance to have reasonable CS values as a check of a safe chamber working point, explain the (limited) effects of CS on Trigger

Detector performance 3) Efficiency

Can we have efficiency vs momentum (statistics) ? If not give the efficiency measured with “high energy” muonsCompare with “timing efficiency” and discuss other contributions.Try to disentangle detector efficiency and acceptance effects.Geometrical acceptance - Hermeticity - Fiducial volume…Compare with MC

Data sample ?

Some material for discussion with some personal comment

Setting up of the detector

Optimization of HV

Time alignment

Multiplicities at HV_optimal.vs.2650V settings

Ratio of the average number of Pads (red) and Clusters (blue) HV_optimal/2650V for noTAE events (time centering for HV_optimal)~ larger V corresponds to lower ratio (M2R1,M3R1), also Clusters change, even if less than Pads

Region M1 M2 M3 M4 M5

Alessia, Rob 23 apr

Effect of HV on clusterShow CS versus HV measured in lab?

Giacomo 16 aprtiming

Detector performance

1) Space alignment

Trigger efficiency - Y misalignments

Stefania muon meeting 23-04-2010

In the Y intercept of fitted track with plane Z=0 we seeA spike of tracks with all Y pads perfectly aligned andmany tracks with not aligned pads trigger inefficiency

1 m

Trigger fails for

Multiple scattering Punch through Decays with large kink

& Detector misalignments

How to spot possible trigger losses due to Y misalignment with stand alone alignment

1) Muon ID with ISMUON (or other equivalent algorithm)2) Select tracks with only 1 hit in M3 (or a cluster of hits

having the same Y)3) Assume the projective slope IP-hitM3 (do not fit θYZ)4) Consider the hits “belonging” to the track and plot ΔMi = YMi – YMiM3 (projective-extrapol from M3 to Mi)

5) Look separately at different regions and side A-C (eventually consider only tracks crossing M3 in the inner

pads of the chambers in regions R1, R2) # For tracks crossing the same region in Mi and M3 Δ = 0 good alignment Δ = ± 1 pad physical misalignment (Mult Scatt…) or detector misalignment If Δ ≠ 0 for M1,M2 no L0mu trigger

YM2-YM3DY = ± ½ pad When tracks change region

DY = ± 1 padMult Scatt ormisalignment

Stefania

R1 R2 R3 R4

R1 R2 R3 R4Y

X

M3

M1

WITH MAGNET ON TRACKS OFTEN CHANGE REGION

A track in M1R3can easily go in M3R4rarely in M3R2 X

Z

M3

M1

R3 R4R2

YM1-YM3 = ± 1/4pad ± 1/2pad rare frequent

Y station alignment w.r.t. M3

when track change region

M3 M3M1 M1

R2 R3

+½ pad DY = ± 1 pad Mult Scatt or misalignment

YM1-YM3

+1pad-1padMisalignment

(n+1-n-1) / n0

With uniform trackdistributions

-½ pad

Stefania

R2 R3

2) Cluster size

8 5 25235.4

Log.pad X (cm)

pys.pad/ log.pad

4

2

R2

R3

R4

M1 M2 M3 M4 M5

2

2

1 1 4 4

0.6

1.3

2.5 12

6.2

3.1 1

1

2

1

1

21

1

1

1

1

WireCath

w

ww

w

w w w ww

2.7 12

1.4 5.8

0.7 2.9

1 1

Walter: COSMICS - CS versus θxz

r/o

MY COMMENTS:

All regions have reasonable values but M2R4 and M3R4Remember that CS are measured in PAD unity smaller values are expected for larger padsFor wire pads we don’t expect large Cluster Size:there is no “induction” and we never measured so high values with cosmics in Lab Compare M2R4 M3R4 with M1M4M5-R4 that have small values as expected M2R4 M3R4 should be much smaller than M2R3 M3R3 (having half pad size and induction)

For collisions 2010 with optimized HV Giacomo reported results compatible with Walter cosmics old HV for all the stations but M2R4, M3R4 where he finds smaller values

COLLISIONS – no angular cut – optimized HVdifferent definition of CS counting both X and Y adjacent hits (angular dependence neglected - is not alwais negligible)

Giacomo 21-05-10

Giacomo

collisions-25ns CS versus θ (θxz woud have been better *)

Giacomo

* θ can be dominated by θyz that is not significant for CS

3) Efficiency / acceptance

stations efficiency stations efficiency 2009 2009 DataData/MC /MC

M1 M1 M2 M3 M4 M5 M2 M3 M4 M5

efficiency (p > 8 efficiency (p > 8 GeV/c)GeV/c)

Muon Meeting – 23/4/2010 P. de Simone 5

to measure the efficiency of M2, M3 and M4 to measure the efficiency of M2, M3 and M4 require the M5 hit in require the M5 hit in x = 4 x = 4

padpadx x

, y = 2 pady = 2 pady y

to measure the efficiency of M5 to measure the efficiency of M5 require the M4 hit inrequire the M4 hit in x = 4 x = 4

padpadx x

, y = 2 pady = 2 pady y

~80% of the selected ~80% of the selected Long TracksLong Tracks are are ’s ’s

x = padx = padx x + 6. x err+ 6. x errxx

y = pady = pady y + 4. x err+ 4. x erryy

search window M2search window M2

x = padx = padx x + 6. x err+ 6. x errxx

y = pady = pady y + 4. x err+ 4. x erryy

search window M3search window M3

x = padx = padx x + 6. x err+ 6. x errxx

y = pady = pady y + 4. x err+ 4. x erryy

search window M4search window M4

x = padx = padx x + 7. x err+ 7. x errxx

y = pady = pady y + 5. x err+ 5. x erryy

search window M5search window M5

x = 5 (padx = 5 (padx x + 6. x err+ 6. x errxx))

y = 3 (pady = 3 (pady y + 4. x err+ 4. x erryy))

search window M1search window M1

Distinguish between detector inefficiency and geometrical effects (acceptance at detector borders and non hermeticity)

Comparison with MCwhere the detector efficiency is plugged in and well known Acceptance effects for M1, M5 (fiducial volume...)

Alessia 19/05/2010Monte Carlo