Triggering MinBias at L 1 Richard Hollis Aneta

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Triggering Min-Bias at L 1 Richard Hollis Aneta Iordanova 4 th December 2006 CMS

Triggering Min-Bias at L 1 Richard Hollis Aneta Iordanova 4 th December 2006 CMS Week Online Selection Meeting

Outline ¢ ¢ Objective Analysis tools Input particle distributions Number of trigger towers l

Outline ¢ ¢ Objective Analysis tools Input particle distributions Number of trigger towers l ¢ ¢ 2 total or transverse energy “Results” Triggering message Heavy-ions Summary Richard Hollis University of Illinois at Chicago 3 rd December 2006 4 th December 2006

Objectives ¢ Study the most effective way to trigger minimum bias events primarily for

Objectives ¢ Study the most effective way to trigger minimum bias events primarily for p+p collisions l for Pb+Pb collisions l • this should be an off-shoot to the p+p work ¢ Need to attain the best efficiency l 3 also consider [rejecting] beam-gas events Richard Hollis University of Illinois at Chicago 3 rd December 2006 4 th December 2006

What is “Min-Bias”? ¢ We consider “Min-Bias” to be all events which undergo an

What is “Min-Bias”? ¢ We consider “Min-Bias” to be all events which undergo an inelastic collision l need not contain a jet! ¢ Mainly soft particle production ¢ Why is it important? l 4 there will be 19 of these mixed in with every CMS event Richard Hollis University of Illinois at Chicago 3 rd December 2006 4 th December 2006

What are “Beam-gas Collision Events”? ¢ Beam-Gas collisions l ¢ inside detector volume interactions

What are “Beam-gas Collision Events”? ¢ Beam-Gas collisions l ¢ inside detector volume interactions with residual gas elements in the beam pipe Not expected to be a large effect l still needs to be considered We (R+A) sometimes refer to these as non-collision events 5 Richard Hollis University of Illinois at Chicago 3 rd December 2006 4 th December 2006

What are “Beam-gas Collision Events”? ¢ Beam-Gas collisions l ¢ interactions with residual gas

What are “Beam-gas Collision Events”? ¢ Beam-Gas collisions l ¢ interactions with residual gas elements in the beam pipe Not expected to be a large effect l 6 outside detector volume still needs to be considered Richard Hollis University of Illinois at Chicago 3 rd December 2006 4 th December 2006

Analysis Tools ¢ ¢ 7 ORCA 8_13_3 used Min. Bias data set (os 05_Py.

Analysis Tools ¢ ¢ 7 ORCA 8_13_3 used Min. Bias data set (os 05_Py. MB) ¢ ¢ Details: Tower Cuts (on E) # trigger tower thresholds Hcal. Trig. Prim: Threshold = 0. 0 Hcal. Trig. Prim: Barrel. ECut = 0. 6 Hcal. Trig. Prim: Endcap. ECut = 0. 8 Hcal. Trig. Prim: Forward. ECut = 1. 5 Richard Hollis University of Illinois at Chicago 3 rd December 2006 4 th December 2006

Particle Distributions ¢ Example: the number of particles initially created hadrons l l l

Particle Distributions ¢ Example: the number of particles initially created hadrons l l l ¢ Pythia Simulation All E>1 Ge. V ET>1 Ge. V Average number of particles with large ET is small Define: “N” side and “P” side 8 Richard Hollis University of Illinois at Chicago 3 rd December 2006 4 th December 2006

Particle Distributions ¢ Example: the number of particles initially created (includes γ, e±) l

Particle Distributions ¢ Example: the number of particles initially created (includes γ, e±) l l ORCA Simulation All Sim. Trk: • close to initial vertex • away from vertex ¢ Additional “secondary” particles which will aid triggering l 9 e. g. come from beam pipe Richard Hollis University of Illinois at Chicago 3 rd December 2006 4 th December 2006

Trigger Towers (E) Test: towers vs Sim. Cal. Hits ¢ l ¢ ORCA Simulation

Trigger Towers (E) Test: towers vs Sim. Cal. Hits ¢ l ¢ ORCA Simulation proportional But: threshold may be too low? l l try: E>10 Ge. V does not change proportionality • lowers offset 10 Richard Hollis University of Illinois at Chicago 3 rd December 2006 4 th December 2006

Trigger Towers (E) Test: towers vs Sim. Cal. Hits ¢ l ¢ ORCA Simulation

Trigger Towers (E) Test: towers vs Sim. Cal. Hits ¢ l ¢ ORCA Simulation proportional But: threshold may be too low? l l try: E>10 Ge. V does not change proportionality • lowers offset 11 Richard Hollis University of Illinois at Chicago 3 rd December 2006 4 th December 2006

Trigger Towers (E) ¢ Optimal Trigger: Towers: N vs P ¢ Strongly correlated ¢

Trigger Towers (E) ¢ Optimal Trigger: Towers: N vs P ¢ Strongly correlated ¢ Trigger should cut on n. Towers hit on “N” side and “P” side l 12 ORCA Simulation e. g. N>10 and P>10 Richard Hollis University of Illinois at Chicago 3 rd December 2006 4 th December 2006

Trigger Towers (E) ¢ Optimal Trigger: Towers: N vs P ¢ Strongly correlated ¢

Trigger Towers (E) ¢ Optimal Trigger: Towers: N vs P ¢ Strongly correlated ¢ Trigger should cut on n. Towers hit on “N” side and “P” side l 13 ORCA Simulation e. g. N>10 and P>10 Richard Hollis University of Illinois at Chicago 3 rd December 2006 4 th December 2006

Optimal Trigger ¢ Count number of towers hit on forward N and P side

Optimal Trigger ¢ Count number of towers hit on forward N and P side HF ¢ Reasoning l forward calorimeter? • helps with possible beam gas rejection • total energy is large in this region l number of towers, not tower energy? • less likely to be “jet biased” from one large energy deposit (see next slides) ¢ 14 Most of all: it is simple Richard Hollis University of Illinois at Chicago 3 rd December 2006 4 th December 2006

Trigger Towers (ET) ¢ Same analysis, this time used ET ORCA Simulation Test towers

Trigger Towers (ET) ¢ Same analysis, this time used ET ORCA Simulation Test towers vs Sim. Cal. Hits ¢ l 15 proportional Richard Hollis University of Illinois at Chicago 3 rd December 2006 4 th December 2006

Trigger Towers (ET) ¢ Same analysis, this time used ET ORCA Simulation Test Towers:

Trigger Towers (ET) ¢ Same analysis, this time used ET ORCA Simulation Test Towers: N vs P ¢ l l correlated lost sensitivity • most signal at 0 or 1 towers hit 16 Richard Hollis University of Illinois at Chicago 3 rd December 2006 4 th December 2006

Trigger Towers (ET) ¢ Same analysis, this time used ET ORCA Simulation Test Towers

Trigger Towers (ET) ¢ Same analysis, this time used ET ORCA Simulation Test Towers Summed energy: N vs P ¢ l l 17 same as using number of towers distribution very spread Richard Hollis University of Illinois at Chicago 3 rd December 2006 4 th December 2006

“Results” Towers cut on total energy Towers cut on transverse energy ε>90% 18 Richard

“Results” Towers cut on total energy Towers cut on transverse energy ε>90% 18 Richard Hollis University of Illinois at Chicago ε≈60% Cuts on ONE Tower 3 rd December 2006 4 th December 2006

Triggering Message ¢ Count towers l need to cut on E for minimum bias

Triggering Message ¢ Count towers l need to cut on E for minimum bias l needs: • 1 bit for yes/no above NTower. Hit (e. g. 5) on both sides l would this vary? or have several bits? • e. g. 1, 5, 10 • this would be useful as we do not know: • physics (much higher multiplicities? ) • detector (hot towers? ) • LHC machine (high beam-gas background? ) ¢ Cutting on ET: l serious reservations as to whether this will work • i. e. would this gain a high enough efficiency 19 Richard Hollis University of Illinois at Chicago 3 rd December 2006 4 th December 2006

Heavy-Ions ¢ We have applied the same logic to Pb+Pb collisions l ¢ 20

Heavy-Ions ¢ We have applied the same logic to Pb+Pb collisions l ¢ 20 b=0 fm Same relative reduction in E and ET l ¢ generator level studies only Hydro Model Calculation compared to total initial particles Number of particles is much larger than minimum bias Pb+Pb collisions Richard Hollis University of Illinois at Chicago 3 rd December 2006 4 th December 2006

Heavy-Ions central ¢ Number of particles in the HF region is large l for

Heavy-Ions central ¢ Number of particles in the HF region is large l for all impact parameters except very peripheral ¢ Line shows p+p @ 14 Te. V expectation ¢ Should get reasonable efficiency even for ET 21 peripheral Richard Hollis University of Illinois at Chicago 3 rd December 2006 4 th December 2006

Summary ¢ Optimal minimum bias trigger read-out total energy l count number of towers

Summary ¢ Optimal minimum bias trigger read-out total energy l count number of towers l • not summed energy l 22 forward calorimeters Richard Hollis University of Illinois at Chicago 3 rd December 2006 4 th December 2006