1. 1 Jet Triggers and Dijet Mass Selda Esen and Robert M. Harris Fermilab TTU Weekly HEP Group Meeting Feb 16, 2006

2. Selda Esen, Fermilab/CU2 Outline Online Selection è Single Jet Trigger Table à Draft in Physics TDR Vol II Benchmark Analysis è Dijet Mass Distribution based on Single Jet Trigger Table à For Phys TDR Vol II Conclusions

3. Selda Esen, Fermilab/CU3 Motivation Define the single jet trigger tables for CMS. è Define the trigger paths from L1 to HLT. è Reasonable thresholds, prescales, and rates at L1 & HLT. è Evolution of the trigger table with time (luminosity) Driven by needs of inclusive jet and dijet mass analysis. è Define trigger needed to make jet E T and dijet mass spectra to search for dijet resonances and contact interactions. è Allows measurement of jet spectra down to low E T or mass to constrain QCD background for realistic searches for new physics. The trigger comes first before analysis. è Wanted to do dijet analysis, but the DAQ TDR trigger was not realistic. è To do analysis we must first define a reasonable trigger.

4. Selda Esen, Fermilab/CU4 Online Selection: Running Periods, Conditions and Samples Pilot Run (2007) è Luminosity = 10 32 cm -2 s -1. Month integrated luminosity ~ 100 pb -1. è L1 allowed rate for single jets ~ 10% of 12.5 KHz / 3 = 0.4 KHz è HLT allowed rate for jets ~ 10% of 100 Hz = 10 Hz 1 st Physics Run (2008 ?) è Luminosity = 10 33 cm -2 s -1. Month integrated luminosity ~ 1 fb -1. è Higher L1 allowed rate for jets (not needed), same HLT rate. “Low Luminosity” running (2008-2009 ?) è Luminosity = 2 x 10 33 cm -2 s -1. “High Luminosity” running (2010 ?) è Luminosity = 10 34 cm -2 s -1. Month integrated luminosity ~ 10 fb -1. 1/8 th of 100 KHz, & safety factor of 3 (from Online PRS)

5. Selda Esen, Fermilab/CU5 Data Sample and Software DC04 actual data samples in Pt intervals: è 0, 15, 20, 30, 50, 80, 120, 170, 230, 300, 380, 470, 600, 800, 1000,1400, 1800, 2200, 2600, 3000, 3500, 4000 è All samples produced with pileup at L = 2 x 10 33 Software: PYTHIA, OSCAR 2_4_5 for sim, ORCA 7_6_1 for digitization è Jet Reconstruction: ORCA_8_7_3 Jets are corrected back to the particles in the jet cone. è Corrections as a function of both jet Et and eta. è L1 Corrections from Frederik Oljemark and Monica Grothe è HLT Corrections from JetCalibV1 in ORCA.

6. Selda Esen, Fermilab/CU6 Online Selection: Trigger Strategy Use corrected jets at L1 & HLT. The limiting rate for jets is at HLT (~10 Hz total). è The allowed HLT jet rate defines the HLT jet E T threshold. We pick an unprescaled jet E T threshold at HLT of roughly 2.5 Hz è For each lum: 10 32, 10 33, and 10 34 è Choose the L1 thresholds at low enough E T so that this HLT threshold will be highly efficient for jets (>95%). We choose additional HLT thresholds at lower E T è With prescales at L1 designed to keep each HLT trigger at 2.5 Hz. HLT 2.5 L1

7. Selda Esen, Fermilab/CU7 Online Selection: Single Jet Trigger Table & Evolution Path L1HLT E T (GeV) Pre- scale Rate (KHz) E T (GeV) Rate (Hz) Low2520000.020602.8 Med60400.0231202.4 High14010.0342502.8 Ultra27010.0144002.6 Ultra27010.0284005.2 Super45010.0136002.8 Trig for L = 10 32 Add for L = 10 33 L = 2 x 10 33 Add for L = 10 34 Jet trigger Evolution: 1)When lum jumps by 10x, add new unprescaled threshold. 2)When lum jumps by 2x, keep same unprescaled threshold. New threshold: Ultra. Raise prescales on Low, Med, and High by 10. Same threshold. Raise prescales on Low, Med, High again by 2. New threshold: Super. Raise prescales on Low, Med, High by 5. Ultra 10. Ultra27010.0144002.6 Ultra27010.0284005.2 Note: we use very little L1 rate

8. Selda Esen, Fermilab/CU8 Online Selection: Trigger Efficiencies at HLT vs. E T High Path L1>140 HLT>250 Ultra Path L1>270 HLT>400 Low Path L1>25 HLT>60 Med Path L1>60 HLT>120 Super Path L1>450 HLT>600 HLTcut We chose the L1 thresholds at low enough E T so that the HLT threshold is highly efficient for jets (>95%)

9. Selda Esen, Fermilab/CU9 Benchmark Analysis: Dijet Mass Distribution Jet Reconstruction & Correction è All analysis with DC04 data samples at Fermilab. è Iterative cone jet algorithm with R=0.5 and E scheme. è Correct jets with jetCalibV1. à Correction back to particles in jet cone before pileup. Event Selection è Find the two jets in the event with highest P T : leading jets.  Require each leading jet have |  | < 1.  Enhances sensitivity to new physics which is produced at low |  |. à Also, Ecal end caps will not be there, on day 1. è Dijet mass: M = sqrt( (E 1 +E 2 ) 2 - (p x1 +p x2 ) 2 – (p y1 +p y2 ) 2 – (p z1 +p z2 ) 2 ). Rates and Cross Section è Plot dijet mass in bins equal to mass resolution: bin size increases with mass. è Divide rate by the luminosity and bin width: differential cross section

10. Selda Esen, Fermilab/CU10 Benchmark Analysis: Event Rates vs. Dijet Mass Trig for 10 32 100 pb -1 Trig for 10 33 1 fb -1 Trig for 10 34 10 fb -1 Event rates demonstrate è Comparable events in each trigger è High statistics overlap between triggers for a given table. è Expect the highest mass dijet to be à ~ 5 TeV for 100 pb -1 à ~ 6 TeV for 1 fb -1 à ~ 7 TeV for 10 fb -1

11. Selda Esen, Fermilab/CU11 Benchmark Analysis: HLT Trigger Efficiency vs. Mass Trigger efficiency is measured for each trigger using the neighboring trigger (lower E T ). We find the mass values that are fully efficient This tells us where we can safely use each trigger, without worrying about trigger systematic errors.

12. Selda Esen, Fermilab/CU12 Benchmark Analysis: Rates for measuring Cross Section Use each trigger where it is fully efficient Stop using the trigger where the next trigger is fully efficient Adequate number of fully efficient events for analysis. Trig for 10 32 100 pb -1 Trig for 10 33 1 fb -1 Trig for 10 34 10 fb -1

13. Selda Esen, Fermilab/CU13 Benchmark Analysis: Dijet Mass Cross Section Put triggers together for dijet mass spectrum. The DAQ TDR trigger roughly corresponds to “Super”: mass > 1800 GeV. The prescaled triggers give us the ability to measure mass down to 300 GeV. è Lower if we can understand efficiency of “Low” Trig Path. | jet  | < 1

14. Selda Esen, Fermilab/CU14 Benchmark Analysis: Dijet Mass Fractional Error (statistical) Trig for 10 32 100 pb -1 Trig for 10 33 1 fb -1 Trig for 10 34 10 fb -1 With increasing luminosity our stat. error at high mass goes down è Improves searches for new physics Statistical error in the region of original triggers (Low, Med, High) remains the same. è 1 – 3% to nail QCD background.

15. Selda Esen, Fermilab/CU15 Conclusions We have defined single jet trigger tables. è The E T thresholds, prescales, and rate estimates at L1 and HLT. è Four running periods: Lum. = 10 32, 10 33, 2 x 10 33 and 10 34 cm -2 s -1. We have a benchmark dijet mass analysis for these triggers è Samples of size 100 pb -1, 1 fb -1, 10 fb -1. We encourage analysis experts to work on the trigger first. è The trigger is the foundation of our analysis capabilities. è Lets make it a strong foundation.