B-Physics Trigger Working Group Status Report http://hepunx.rl.ac.uk/atlasuk/simulation/level2/meetings/AweekFeb01/ Bphys210201.ppt Bphys210201.pdf Bphys210201.ps John Baines
B-trigger selections at LVL2 and EF
EF rates, status at end 2000
Tighter cuts for D s selection
J/ rate v. p T threshold
Example of rates with tighter cuts
Example B-Physics Trigger Menu
Level 2 : Confirm muon
ID full-scan require additionally:
Second p T > 3-5 GeV or
electron p T > 5 GeV or
Reconstruct characteristic decay products e.g.:
e e pair, J/ ee invariant mass window
3 hadrons, 0 (KK) and D s (KK ) mass
2 hadrons, B d ( ) mass window
Level 1 : muon p T > 6 GeV
EF: Re-do ID recon. using offline-type algorithms:
Apply tighter cuts to J/ ee D s (KK ), B d ( )
Apply cuts to select J/ LVL2 and -e triggers)
Use offline-type cuts for rare decay channels (accepted
by LVL2 trigger).
bb eX B d (J/ ( )K 0 ) bb X B d (J/ (ee)K o ) bb X B d (J/ (ee)K o ) B d B d J/ ( )(K/K*) B s J/ ( ) B B K 0 * , etc. b 0 J/ ( ) B c J/ ( )
Better track resolution Tighter Mass cuts
Vertex fit cuts on 2 , decay length,
angular cuts based on event topology
B B K 0 * , etc. B s D s B s D s a 1 D s o , o K K To be studied further.
B-physics Trigger Rates Status at TDAQ Week Nov 2000
Events with direct J/ ( ) and J/ (ee) are also needed, however these can be pre-scaled.
Rates subject to uncertainties in cross-sections & muon rates.
Physics programme and trigger menu will evolve with time up to and after LHC switch-on.
EF rate estimates are based on offline code. In particular K/ rejection at EF (and LVL2) has to be
demonstrated with algorithms suitable for EF (LVL2).
Work is continuing on EF selections for B d,s - > X channels.
Level-2 6 + 5 6 + e5 6 + B( ) 6 + D s ( (KK) 6 + J/ (ee) Total (B-physics triggers) 100 Hz 50 Hz 50 Hz 150 Hz 200 Hz 550 Hz muon p T >6 Level-1 23 kHz muon p T >6 (ID+muon) Level-2 5 kHz EF B d,s - > (X) ( p T >6) J/ - > 6 + B( ) 6 + D s ( (KK) 6 + J/ (ee) Total (B-physics triggers) small 10 Hz 5 Hz 25 Hz 20 Hz 60 Hz muon p T >6 (ID+muon) EF 5 kHz
B d Trigger Efficiency for B events with pile-up (L = 10 33 cm -2 s -1 ): 78% : B events, p T ( , ) > 4 GeV 93% : B events selected offline 0.93% : Background B X events Level-2 rate ~50 Hz for 5 kHz 6 EF selection reduces rate to ~5 Hz
Event Filter Selection:
Tighter mass cut
Vertex fit cuts :
2 / N d.o.f. < 8,
L xy > 100 m,
xy < 5
Tracks separated from trigger by R > 0.2
p T > 3.9 GeV
Two opposite sign tracks with:
p T + p T > 10 GeV
z 0 < 2 cm
4.3 < M( ) < 6.3 GeV
+ - xy L xy Decay Vertex 10 15 20 25 30 35 40 45 50 p T of B d (GeV) B d p T spectrum both p T >4 GeV 100 80 60 40 20 0 Level-2 Efficiency (%) x y LVL2 0 2 4 6 8 M( (GeV) Signal Events + min. bias
D s Trigger o
Tracks: p T > 1.4 GeV
R > 0.2 w.r.t. trigger
EF Event Selection:
Tracks: p T > 1.5 GeV
Mass cuts :
M(KK) - M( ) < 14 MeV
M(KK ) - M(D s ) < 56 MeV
vertex fit cuts:
2 prob. >0.5%, L xy > 200 m
D s vertex fit :
2 prob. >0.5%, L xy > 200 m
Two opp. sign tracks satisfying:
M(KK) - M( ) < 17 MeV (~3 trigger )
Third track with:
M(KK ) - M(D s ) < 74 MeV (~3 trigger )
New selection cuts by Innsbruck
Level-2 Efficiencies for
B s D s ( (KK)) events with pile-up
(L = 10 33 cm -2 s -1 ):
58% : Signal events with
p T ( , and K) > 1.5 GeV
63% : Signal events selected offline
3% : Background B X
Level-2 Trigger rate ~150 Hz
for 5 kHz 6
EF selection reduces rate to
21 Hz 4 offline mass cuts
17 Hz 3.5 offline mass cuts
13 Hz 3 offline mass cuts
for 5 kHz 6
offline ( ) = 3.4 MeV
offline ( D s ) = 14 MeV
Effect of higher muon p T threshold: D s (KK) trigger Study by Innsbruck of impact of raising muon p T threshold on D s (KK) trigger Signal efficiency falls of fairly rapidly, more rapidly than background.
J/ e e Trigger
Event Filter Selection:
Tighter mass cuts
Vertex fit cuts :
2 / N d.o.f. < 8,
L xy > 220 m,
xy < 40
Two opposite-sign e tracks with:
p T + p T > 4 GeV
| | < 1.4, | z 0 | < 2 cm
cos( ee ) > 0.2
2 < M(ee) < 3.5 GeV
Tracks: p T > 0.5 GeV
Identified as electrons by TRT
Level-2 Efficiencies for B d J/ (ee)K s events with pile-up (L = 10 33 cm -2 s -1 ): 44% : Signal events with p T (e,e) > 1.5 GeV 57% : Events selected offline 4% : Background B X events Level-2 Trigger rate ~200 Hz for 5 kHz 6 EF selection reduces rate to ~20 Hz o Signal Events + Min. Bias 0 1 2 3 4 5 M(ee) (GeV) LVL2
Effect of electron p T Threshold 25 20 15 10 5 0 Rate (Hz) Signal Efficiency (%) Efficiency for B d - > J/ (ee) K 0 ( ) Rate for B - > X + pile-up for 5 kHz 6 rate p T cut (GeV) p T cut (GeV) 0.5 1.0 1.5 2.0 2.5 3.0
Study by Moscow of effect of raising
p T threshold for e in J/ (ee) trigger
Further rate reduction, with some loss of
physics, e.g. :
Raising p T cut from 0.5 GeV to 0.8 GeV
Rate reduced from 17 Hz to 8 Hz
4% efficiency loss for B d - > J/ (ee) K 0
100 80 60 40 20 0 0.5 1.0 1.5 2.0 2.5 3.0
B-physics Trigger Rates - Example of tighter cuts muon p T >6 (ID+muon) EF 5 kHz
Tightening D s and mass cut gives negligible signal loss provided the same mass resolution can be achieved at the EF as offline => need to assess impact of calibration, availability of survey info and impact of any speed-up of algorithms c.f. offline. Similarly for other “offline-type” selections.
small 10 Hz 5 Hz 13 Hz 10 Hz 38 Hz 5 kHz Notes: Assuming offline-type selection Estimate (conservative?) (Signal ~2 Hz, Bg about same) Rounded up from 3 Hz from Flora Mass cuts tightened to 3 offline add transverse decay length cut.. p T threshold raised to 0.8 GeV => 4% signal loss. EF B d,s - > (X) ( p T >6) J/ - > 6 + B( ) 6 + D s ( (KK) 6 + J/ (ee) Total (B-physics triggers) small 10 Hz 5 Hz 25 Hz 20 Hz 60 Hz
LVL2 Robustness Studies Misalignment ( m) Misalignment ( m) 1 10 100 1000 1 10 100 1000 90 80 70 60 50 40 Efficiency (%) D s (MeV) 60 40 20 Effect of Pixel Barrel Misalignment on B( ) trigger Effect of SCT barrel Misalignment on D s ( (KK) ) trigger Fraction of Hits/Spacepoints deleted 60 50 40 30 Efficiency (%) 0.001 0.01 0.1 Effect of inefficiency on D s ( (KK) ) trigger Pixel Barrel 15 30 Endcap 50 100 Limits on R precision ( m) for signal loss <2% <5% SCT Barrel 60 100 Endcap 80 100
Future Work - Robustness
Extend LVL2 robustness studies to J/ channel including TRT
Compare robustness of TRT-guided c.f. pixel-guided reconstruction for J/
Look at EF selection, expected to be more sensitive than LVL2 due to:
vertex fit quality cuts
transverse decay length cuts
tighter mass cuts
Easter 2001 Moscow End 2001?? Who?? Easter 2001 Moscow
Future Work - LVL2
Repeat B-trigger measurements including muon simulation (previously used Kine).
Effect of New layouts:
- evaluate effect of latest ID layout (Insertable pixel layout).
LVL2 Algorithm Development :
Scan of pixels+SCT (more robust than pixel-scan) two techniques:
- based on pixel-scan : Genova
- based on hit filtering algorithm + kalman fitter : Nikos
Vertex reconstruction at LVL2 - Nikos?
Reproduce cTrig functionality in new framework
Add new functionality in new framework:
and e reconstruction in ID RoI
Need new data-sets => Spring 2002?? Time-scales set by PESA s/w group - September 2001 Autumn 2001?? All Need muon code and new data-sets. Probably use new framework => Mid 2002 Autumn 2002? End 2001?
Future Work - EF Selection
EF Selections :
Investigate EF selections for B - > X channels
Check compatibility of cuts with offline selections, particularly background estimations, systematic bias etc.
Check effects of layout changes
Timing measurements for B-selections, development of algorithms suitable for EF (ID, Muon, Calorimeter reconstruction).
Pythia studies : Easter 2001 September 2001?? Need new data-sets => Spring 2002?? Need all algorithms in new framework Mid 2002?? Moscow, Innsbruck? Full simulation - needs data-sets => End 2001?? Moscow (Nikolai) B Physics WG Who??
Datasets with ID ‘insertable’ layout, modular TRT, true solenoid B-field:
Single particle datasets for tests
Whole detector (incl. muons):
Signal datasets :
6 + B ,
6 + B D s B D s a 1 ,
6 + B J/ (ee),
B J/ ( 6, ),
Background : B X
Datasets for studies with and e in LVL2 RoI from ID:
6 + B J/ (e5e)
e5 + B J/ ( 6, )
B J/ ( 6, )
Easter 2001? Autumn 2001?? End 2001??
B-trigger Workplan 2002 2001 Mar Apr May Jun Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Pythia studies EF: B (X) full sim. studies EF Timing Timing for B selection J/ , TRT Robustness EF Robustness studies Algorithm develop. Pixel scan incl. SCT LVL2 vertexing Studies in New f-w cTrig Functionality New s/w Reconstruct e in RoI from ID Reconstruct in RoI from ID repr. TP results verify TP - new layout add LVL1 + LVL2 mu TP results + mu Full B-menu ID sngl prt Dataset Prd. New layout Sig. & bg all det.
D s ( (KK) ) trigger: tighter EF cuts studied => ~halving of rate.
Effect of raising muon p T thresholds studied, but signal efficiency falls rapidly
J/ (ee) trigger: raising e p T threshold studied, can ~halve rate for 4% signal loss.
LVL2 Trigger robust w.r.t. SCT misalignment.
Pixel R misalignment limit: 15 m (barrel).
Trigger robust w.r.t. SCT inefficiency.
Main concern is impact of dead pixels on pixel-scan efficiency, but a new more robust algorithm is being developed.
Studies will be extended to the J/y(ee) trigger and TRT
Studies will be extended to EF if someone can be found for this work.
Algorithm development is continuing. Vertex finding at LVL2 will be investigated.
Studies started for EF selection for B (X), initially at the particle level.
Future work will be focussed on:
new data-sets with the whole detector and updated ID layout.
additional functionality in the new s/w framework leading to a simulation of the complete B-physics trigger menu ~end 2002.