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Selection of non-triggering muons in J/ψ μμ events for the calibration of the Muon System

1) Offline Selection: use of Mass Constrained Global Fit (thanks to Stefania Vecchi for the help!)

2) Online Selection: Modification of the single muon line in order to increase the rate

G. Lanfranchi – May third, 2006

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Main steps:

1) Pick up events from single muon line (as it is now)2) Identify the muon which provides the trigger3) Search for a second long track of opposite charge wrt the triggering muon4) Do the mass-constraint-global fit imposing the J/Psi mass 5) Select events with a chi2 < cut6) Evaluate the purity of non-triggering muons

I have used (for the moment): - 50000 Bd J/Psi(mu+ mu-) Ks events - DaVinci v12r15 - HltGeneric v2r8

1) Offline selection using a mass-constrained global fit

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Pt distribution BEFORE Pt cut

N = 42794<Pt> ~ 2.3 GeV

Pt (GeV/c)

Pt distribution AFTER Pt cut

1) Pick up events from the single muon linestandard single muon line requires a muon with Pt> 3GeV, IPS>3Pt distributions of triggering muon:

Pt (GeV/c)

Comment: Pt > 3 GeV is a quite strong cut : do we really need it?

N = 9329

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2) Identify the muon which provides the trigger

Pt (trigger)-Pt (Offline) (MeV/c)

N = 7778

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4) Mass Constrained Global Fit for B J/Psi (μμ) X (I)

π

π-

SV

(x+, y+, tx+, ty+, p+)

(x-, y-, tx-, ty-, p-)

(xo, yo, z0)

@ z

MJ/ψ (x,y,tx,ty,p)

PV(xPV,yPV,zPV)

By means of Lagrange-multiplier method the constrained least square is minimized and “best” parameters are found.

Measured quantities: x,y,tx,ty,p for each muon (5x2 = 10)Constraints : 4 – momentum conservation (4) J/Psi, mu+ and mu- from the same vertex (3x2 =6) total = 10Fitted parameters: J/Psi vertex position (3) J/Psi x,y,tx,ty,p (5)NdF = Constraints – parameters = 2

See S. Vecchi talk, LHCb Italia Meeting, Florence 2006http://indico.cern.ch/conferenceDisplay.py?confId=1457

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χ2 <100 N = 7778 χ2 < 50 N = 6549 χ2 <10 N = 4903

μ+μ- invariant mass vs χ2 cut χ2 distribution of the global fit

χ2<10 χ2<50 χ2<100

Mass Constrained Global Fit for B J/Psi (μμ) X

M(μμ) (MeV/c2)

the χ2 cut cleans up the sample ! J/Psi mass peak shows up without tails

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χ2 <100 χ2 < 50 χ2 < 10

χ2 <100 χ2 < 50 χ2 <10

Momentum Distribution for Triggering and Non-Triggering Muon

Triggering muon: Non-Triggering muon:

Non-triggering muon has a spectrum in the whole range of interest:Above 150 GeV there are few events but the efficiency is also highso we need less statistics to evaluate it!

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Pt Distribution for Triggering and Non-Triggering Muon

χ2 <100 χ2 < 50 χ2 <10

χ2 <100 χ2 < 50 χ2 <10

Triggering muon: Non-Triggering muon:

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Pt and P distributions of triggering (red)-non triggering (blue) muons

P (GeV/c)Pt (GeV/c)

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Purity = N. of true muons / N. of selected muons Pt distribution for “ true” muonsand “selected” muons

<Purity> ~ 88% for 0<p<100 GeV/c

Purity of the selected calibration sample for chi2 < 10

P (GeV/c)Pt (GeV/c)

“true”

“selected”

For Pt > 0.7 GeV almost all the selected muons are true muons from J/Psi

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Purity vs P

<purity>~96%From 1 -100 GeV/c

<Purity> ~ 97% for 0.7 < p < 100 GeV/c

Purity of the selected calibration sample for χ2 < 10 and Pt>0.7 GeV/c

Momentum distribution:

“true”

“selected”

P (GeV/c) P (GeV/c)

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1) With the two cuts χ2 < 10 and Pt>0.7 GeV we get, from the single muon line, a calibration sample with a purity of 97% and momentum spectrum which covers all the interesting range.

2) I used B J/ψ(μμ) Ks events, BUT no assumption has been made on Ks: We can use the same selection for all the BJ/ψ(μμ) X decay modes

3) The game must be repeated with bb-inclusive sample to evaluate the S/B ratio: BUT we can tighten the χ2 cut to recover the same purity.

Comments (I) :

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Comments (II) :

The problem is the rate:

1) from 50000 generated events we endup with ~ 3800 events;

2) total efficiency Eff ~ 8% for Bd J/Psi(μμ) Ks events (acceptance x L0 x L1 x HLT single muon line x identification of triggering muon x χ2 cut x Pt cut) : Rate = σ (bb) x L x f(Bd,Bs,B+) x BR(BJ/ψ (μ) X) x Eff ~ 500 μb x 2x1032 cm-2 s-1 x 90% x 2x10-4 x 8% ~ 1.4 Hz

3) I expect that the efficiency will go down if we analyze bb-inclusive and we want recover the same purity.

4) So we will endup with a rate ~ 1 Hz, probably less !!

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A PROPOSAL FOR A MODIFICATION OF THE SINGLE-MUON LINE IN HLT( idea already presented at LHCb Italia Meeting in Florence, April 2006 )

1. Start from events with the standard single muon line cuts: one “online recognized muon” with pt>3 GeV/c, the cut in IPS to be defined (use also J/Psi prompt?)

2. Loop on long triggertracks and select the first one with opposite charge which comes from the same vertex (trgvertexfit χ2 < 5 );

3. Filter the events if the Muon track and the second track give a J/Psi invariant mass between a certain range.

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Pt distribution BEFORE Pt cut

N = 42794<Pt> ~ 2.3 GeV

Pt (GeV/c)

Pt distribution AFTER Pt cut

standard single muon line requires a muon with Pt> 3GeV, IPS>3Pt distributions of triggering muon:

Pt (GeV/c)

N = 9329

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χ2 distribution of the vertex fit for events after Pt and IPS cut

Events with χ2<5 and2.5 GeV<M(J/Psi)<3.5 GeV

N = 7242

Eff = 7242/9329 ~ 80%

The algorithm works with high efficiencyBut…. What about speed?

χ2/ ndf

M(J/Psi (μμ)) (MeV/c2)

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Generic and Specific HLT:Use 1/4 of 1600 CPUs at 40 kHz: 10 ms/event on a 2007 CPU. Assume 60 ms on a 1 GHz Pentium III

1 GHz Pentium III

Execution Average

VeLo Tracking 7 ms 7 ms

Generic HLT 19 ms 19 ms

Rest of Forward Tracking 15 ms 5 msPID (mainly RICH) 35 ms 12 ms

Shared Resonances 12 ms 4 msD* stream 1 ms < 1 ms

Exclusive stream 9 ms 3 msTotal N/A 50 ms

HLT speed requirements

P.Koppenburg, LHCC Comprehensive Review, January 2005

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ToolSvc.SequencerTimerTool INFO ------------------------------------------------------------------------------------------------ToolSvc.SequencerTimerTool INFO This machine seems about 1.01 times faster than a 2.8 GHz Xeon.ToolSvc.SequencerTimerTool INFO Algorithm (millisec) | <user> | <clock> | min max | entries | total (s) |ToolSvc.SequencerTimerTool INFO ------------------------------------------------------------------------------------------------ToolSvc.SequencerTimerTool INFO DaVinciMainSeq | 68.772 | 92.957 | 22.324 799.5 | 456 | 42.389 |ToolSvc.SequencerTimerTool INFO DaVinci | 0.733 | 0.996 | 0.831 22.6 | 300 | 0.299 |ToolSvc.SequencerTimerTool INFO OldRichPIDCnvAlg | 6.533 | 9.120 | 2.036 33.1 | 300 | 2.736 |ToolSvc.SequencerTimerTool INFO MuonIDFOI | 16.000 | 21.783 | 5.297 96.9 | 300 | 6.535 |ToolSvc.SequencerTimerTool INFO ChargedProtoPAlg | 36.833 | 49.436 | 11.160 646.2 | 300 | 14.831 |ToolSvc.SequencerTimerTool INFO PrimVtxFinder | 5.667 | 6.591 | 0.734 646.1 | 300 | 1.977 |ToolSvc.SequencerTimerTool INFO HLTGenericSeq | 12.615 | 13.809 | 3.247 77.3 | 130 | 1.795 |ToolSvc.SequencerTimerTool INFO TrgMuonRec | 0.538 | 0.385 | 0.090 2.7 | 130 | 0.050 |ToolSvc.SequencerTimerTool INFO Load from Buffer | 0.000 | 0.056 | 0.031 0.5 | 130 | 0.007

ToolSvc.SequencerTimerTool INFO Make pad from strip | 0.078 | 0.061 | 0.010 0.8 | 386 | 0.023 |ToolSvc.SequencerTimerTool INFO Reconstruct muons | 0.078 | 0.024 | 0.002 0.5 | 386 | 0.009 |ToolSvc.SequencerTimerTool INFO Store muons | 0.077 | 0.036 | 0.002 0.5 | 130 | 0.005 |ToolSvc.SequencerTimerTool INFO HltMuonRec | 0.077 | 0.090 | 0.019 0.7 | 130 | 0.012 |ToolSvc.SequencerTimerTool INFO Associate muons | 0.077 | 0.072 | 0.003 0.6 | 130 | 0.009 |ToolSvc.SequencerTimerTool INFO HltGenericSelection | 0.154 | 0.222 | 0.076 2.7 | 130 | 0.029 |ToolSvc.SequencerTimerTool INFO GenMakeTTHit | 0.846 | 0.811 | 0.187 2.4 | 130 | 0.105 |ToolSvc.SequencerTimerTool INFO GenVeloTT | 1.385 | 1.437 | 0.300 6.2 | 130 | 0.187 |ToolSvc.SequencerTimerTool INFO TrgMuonRecover | 0.000 | 0.026 | 0.014 0.5 | 130 | 0.003 |ToolSvc.SequencerTimerTool INFO GenMakeTHit | 0.846 | 1.429 | 0.343 9.1 | 130 | 0.186 |ToolSvc.SequencerTimerTool INFO GenForward | 7.923 | 7.942 | 0.727 56.2 | 130 | 1.033 |ToolSvc.SequencerTimerTool INFO TrgMuonRefine | 0.077 | 0.040 | 0.017 0.4 | 130 | 0.005 |ToolSvc.SequencerTimerTool INFO GenErrParam | 0.077 | 0.038 | 0.024 0.1 | 130 | 0.005 |ToolSvc.SequencerTimerTool INFO GenParticleMaker | 0.231 | 0.333 | 0.198 1.8 | 130 | 0.043 |ToolSvc.SequencerTimerTool INFO HltGenericDecision | 0.462 | 1.031 | 0.604 5.3 | 130 | 0.134 |ToolSvc.SequencerTimerTool INFO AnaJpsiLine Timer | 0.000 | 0.183 | 0.096 0.6 | 130 | 0.024 |ToolSvc.SequencerTimerTool INFO AnaMuonLine Timer | 0.077 | 0.132 | 0.056 0.7 | 130 | 0.017 |ToolSvc.SequencerTimerTool INFO AnaL1Conf Timer | 0.077 | 0.027 | 0.003 0.4 | 130 | 0.003 |ToolSvc.SequencerTimerTool INFO AnaSndVtx Timer | 0.000 | 0.030 | 0.007 0.6 | 130 | 0.004 |ToolSvc.SequencerTimerTool INFO ------------------------------------------------------------------------------------------------

Official Single Muon Line

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ToolSvc.SequencerTimerTool INFO ------------------------------------------------------------------------------------------------ToolSvc.SequencerTimerTool INFO This machine seems about 0.99 times faster than a 2.8 GHz Xeon.ToolSvc.SequencerTimerTool INFO Algorithm (millisec) | <user> | <clock> | min max | entries | total (s) |ToolSvc.SequencerTimerTool INFO ------------------------------------------------------------------------------------------------ToolSvc.SequencerTimerTool INFO DaVinciMainSeq | 69.101 | 121.609 | 25.970 3238.3 | 456 | 55.454 |ToolSvc.SequencerTimerTool INFO DaVinci | 0.967 | 1.559 | 0.822 99.6 | 300 | 0.468 |ToolSvc.SequencerTimerTool INFO OldRichPIDCnvAlg | 6.467 | 12.381 | 2.300 163.1 | 300 | 3.714 |ToolSvc.SequencerTimerTool INFO MuonIDFOI | 16.067 | 28.587 | 5.267 349.8 | 300 | 8.576 |ToolSvc.SequencerTimerTool INFO ChargedProtoPAlg | 36.500 | 66.010 | 14.425 2624.9 | 300 | 19.803 |ToolSvc.SequencerTimerTool INFO PrimVtxFinder | 6.233 | 9.700 | 0.694 1313.9 | 300 | 2.910 |ToolSvc.SequencerTimerTool INFO HLTGenericSeq | 13.231 | 15.338 | 3.338 110.7 | 130 | 1.994 |ToolSvc.SequencerTimerTool INFO TrgMuonRec | 0.231 | 0.398 | 0.123 2.7 | 130 | 0.052 |ToolSvc.SequencerTimerTool INFO Load from Buffer | 0.077 | 0.061 | 0.031 0.5 | 130 | 0.008 |ToolSvc.SequencerTimerTool INFO Make pad from strip | 0.000 | 0.061 | 0.010 0.7 | 386 | 0.024 |ToolSvc.SequencerTimerTool INFO Reconstruct muons | 0.026 | 0.025 | 0.002 0.4 | 386 | 0.009 |ToolSvc.SequencerTimerTool INFO Store muons | 0.000 | 0.038 | 0.002 0.5 | 130 | 0.005 |ToolSvc.SequencerTimerTool INFO HltMuonRec | 0.077 | 0.090 | 0.017 0.7 | 130 | 0.012 |ToolSvc.SequencerTimerTool INFO Associate muons | 0.000 | 0.072 | 0.003 0.6 | 130 | 0.009 |ToolSvc.SequencerTimerTool INFO HltGenericSelection | 0.154 | 0.533 | 0.076 42.5 | 130 | 0.069 |ToolSvc.SequencerTimerTool INFO GenMakeTTHit | 0.923 | 0.892 | 0.195 6.7 | 130 | 0.116 |ToolSvc.SequencerTimerTool INFO GenVeloTT | 1.462 | 1.780 | 0.296 37.0 | 130 | 0.231 |ToolSvc.SequencerTimerTool INFO TrgMuonRecover | 0.000 | 0.026 | 0.014 0.5 | 130 | 0.003 |ToolSvc.SequencerTimerTool INFO GenMakeTHit | 1.385 | 1.523 | 0.411 8.5 | 130 | 0.198 |ToolSvc.SequencerTimerTool INFO GenForward | 7.462 | 8.197 | 0.722 55.6 | 130 | 1.066 |ToolSvc.SequencerTimerTool INFO TrgMuonRefine | 0.000 | 0.043 | 0.019 0.4 | 130 | 0.006 |ToolSvc.SequencerTimerTool INFO GenErrParam | 0.000 | 0.038 | 0.023 0.1 | 130 | 0.005 |ToolSvc.SequencerTimerTool INFO GenParticleMaker | 0.462 | 0.355 | 0.201 1.8 | 130 | 0.046 |ToolSvc.SequencerTimerTool INFO HltGenericDecision | 1.077 | 1.429 | 0.624 57.7 | 130 | 0.186 |ToolSvc.SequencerTimerTool INFO AnaJpsiLine | 0.308 | 0.183 | 0.100 0.5 | 130 | 0.024 |ToolSvc.SequencerTimerTool INFO AnaMuonLine | 0.000 | 0.135 | 0.061 0.8 | 130 | 0.018 |ToolSvc.SequencerTimerTool INFO AnaL1Conf | 0.077 | 0.100 | 0.003 9.8 | 130 | 0.013 |ToolSvc.SequencerTimerTool INFO AnaSndVtx | 0.077 | 0.030 | 0.008 0.6 | 130 | 0.004 |ToolSvc.SequencerTimerTool INFO ------------------------------------------------------------------------------------------------

New Single Muon Line:

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Comments :

1. The algorithm itself does not introduce any consistent delay (new single muon line = 135 μsec old single muon line = 132 μsec

2. The difference overall in the HltGenericDecision is 300-400 μsec mainly due to the retrieving of the trigger tracks this can be further optimized.

3. The efficiency in selecting muons from BJ/Psi X is quite high, of the order of ~80%.

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Next Steps:

1) Reduce the IPS cut on the single muon to select J/Psi prompt and tighten the Invariant Mass window in order to maintainthe bandwidth at a reasonable level.

2) Study with the Offline Procedure the purity, the efficiency, theS/B ratio of this new sample.

3) Since σ (J/ψ prompt) ~ 10 x σ (J/psi from B) we expect to havea total rate of 10-15 Hz of J/Psi prompt events fully negligible with respect to the single muon line (~ 900 Hz)and the di-muon line (~600 Hz).

4) Hans Dijkstra is fully open to accept our requests if they are reasonable. we have to present our proposal at a T-Rec meeting within May I am available – as soon as I am ready – to give a talk to the whole Muon Group in order to explain all the details.

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Issues to be discussed:

1) As soon as we will have new tracks for DC06 production we must be ready to recalibrate MuonID and Pion misID as soon as possiblesince stripping needs PID from all the subdetectors. It could be worth to do in both ways: a) the old one : calibration of FOI and DIST using MC truth b) the new one: using selected muons for calibrationand compare the results.

Erica and Miriam: have you this procedure ready? Can you help me to do the same using calibrating muons?

2) Could we use only the DIST variable instead of the FOI+DIST?It would simplify quite a lot the whole procedure…Did you try already in the past?

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3) We must provide an exact estimate of how many events we will need to calibrate the Offline MUONID. Do you confirm the 100k of “pure” muons? Can you provide some quantitative result? How many events do you think that we would need for calibrating the DIST variable only ?

4) Is somebody looking at the D* inclusive sample for calibration of Pion misID?

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5) What is the meaning of “Muon” and “NotMuon” DLL values?C. Jones talk at the last Software Week

6) Other issues ??