Efficiency of the CMS Level-1 Trigger to Selected Physics Channels by: Corey Sulkko Faculty Mentor: prof. Darin Acosta Funded by: National Science Foundation Presentation overview Overview of CMS experiment The importance of the Level-1 Trigger to CMS Methods of calculating the efficiency of the Level-1 Trigger Results Future Research Overview of the CMS Experiment The Standard Model predicts a particle not yet found, the Higgs Boson the Higgs is expected to be very massive, and because E mc2 , it needs high energy collisions to be created Currently the Tevatron collides particles at 2 trillion electron volts, which may not be enough energy to create the Higgs, which leads us to the Large Hadron Collider at CERN the Large Hadron Collider the LHC the Large Hadron Collider will be used to collide protons at 14 TeV, which we think may be enough energy to create many Higgs particles for study To find the Higgs, we will try to reconsruct the particles that it decays into, by using the momenta of these reconstructed particles we can calculate the mass of the Higgs Since a couple of Higgs decays modes go into muons, we will use a muon detector... the Compact Muon Solenoid Compact Muon Solenoid detector Solenoid provides magnetic field to measure momentum of particles, which can be used to calculate their masses UF works with the endcap detectors and Trigger system endcap detectors Endcap detectors use Cathode Strip Chamber(CSC) detectors The CSC’s are trapezoidal and each contain six layers of detection, they are arranged overlapping each other to form a circular disc Each endcap consists of four discs CSC contains gas mixture which ionizes when a muon passes through, electrons are collected on high voltage wires, signals induced on perpendicular cathode strips Using reconstructed paths to calculate transverse momentum of muon By knowing where the muon hit on each of the four CSC’s, we can reconstruct the path that the muon took Knowing the change in the angle , the transverse momentum(Pt, the momentum in the direction of the change in the angle ), the mass can be calculated the Level-1 Muon Trigger Since the LHC will be colliding p’s at 40,000,000 per second, something is needed to filter out muons with low Pt’s, because they couldn’t have possibly come from the massive Higgs particle, otherwise there would be too much data to analyze(1 megabyte per collision) The CSC detectors create electronic signals, something is needed to reconstruct the tracks and calculate the Pt of the muons the Level-1 Muon Trigger(L1T), under design at UF, does these two things Efficiency of the Level-1 Trigger The efficiency of the L1T is the fraction of time that the trigger reconstructs a particle in the endcap region that was produced in that region. To select is to allow the particle to be stored for future analysis The L1T is the first of a 3 level trigger system being designed for the CMS endcaps Because the Higgs is expected to be created less than once every trillion collisions, we want the efficiency for these particles to be as high as possible. Physicists will set the Trigger so that it selects all events that generate muons above a certain Pt Calculating the Efficiency of the Trigger run simulations of the collisions, the detectors, and the Trigger calculate the efficiency Signal MB Detection CMSIM HEPEVT ntuples Zebra files with HITS Objectivity Database ORCA ooHit Formatter Objectivity Database HLT Grp Databases HLT Algorithms New Reconstructed Objects Objectivity Objectivity ytivitcejbO Database Database esabataD Mirrored Db’s Catalog import (CERN, US, Italy,…) Triggering Objectivity Database ORCA Digitization (merge signal and MB) ORCA Prod. Catalog import MC Prod. Collisions Simulating the Experiment Simulate the Collisions Use an event generator program to simulate the particle collisions. Pythia simulates particle collisions and decays based on the rules of quantum mechanics Set the generator to produce only the decays you are interested in pp -> H -> ZZ -> µµµµ, pp -> H -> WW -> µµ B -> J/y -> µµ Generate many events Simulate the detection and the Level-1 Trigger behavior Simulated detection using the program CMSIM simulates the behavior of the particles as they move through the material of the CMS detector Used ORCA to simulate the response of the detectors and to simulate the behavior of the L1T in response to the digitized data from the detectors ORCA stores the information about the particles produced by the collision, the generated data, and the results as interpreted by the L1T all in a binary file This file can then be analyzed using the graphical analysis program ROOT Results ROOT was used to calculate the efficiency of the L1T to select 1, 2 and 3 muon events for three different Pt Thresholds: Pt > 0, Pt > 10, and Pt > 25 GeV/c This was done for all three decays For the Higgs decays this was done for 6 different Higgs masses between 125 and 250 GeV For J/Psi we simulated minbias proton collisions The probability of generating 1 or more, 2 or more, and 3 or more muons was also calculated for the three diffirent Pt thresholds and six diffirent masses Efficiency of the L1T to select 1 and 2 muon events as a function of Higgs mass for select Higgs decays Results from the H WW u+ u- events were very similar: in almost all cases within at least .05 of the values for HZo Zo u+ u- u+ u- Efficiency of the L1T to select 1 or 2 muon events for minbias B -> J/y -> µµ decays The efficiency of the L1T to select muons from B -> J/y > µµ decays was found to be much lower This is because the Higgs boson has a higher mass then the j/Psi, and is therefore easier to detect at higher Pt’s Efficiency to select J/Psi decaying to 2 mu for different Pt ranges and number of particles generated in endcap Pt >= 0 Pt >= 10 Pt >= 25 1 mu in .844 +/- .011 .232 +/- .013 .035 +/- .006 endcap 2 mu in .689 +/- .015 .067 +/- .008 0.00 endcap Probability of generating 1, 2, or 3 or more muons in the endcaps as a function of mass for H Zo Zo u+ u- u+ u About 80% of all H Zo Zo u+ u- u+ u events had at least 1 muon go into the endcap Probability of generating 1, 2, or 3 or more muons in the endcaps as a function of mass for H W+ W- u+ u- About 50% of all H W+ W- u+ u- events had at least 1 muon go into the endcap Probability of B -> J/y -> µµ generating one or two muons in the endcap The probability if B -> J/y -> µµ producing 1 or more muons in the endcaps was found to be about 27% Probability of J/Psi generating one or two muons in the endcap Pt >= 0 Pt >= 10 Pt >= 25 1 or more mu’s .27 +/- .014 .015 +/- .004 0.00 in endcap 2 or more mu’s .05 +/- .007 0.00 0.00 in endcap Future Research The L1T is the first in a series of three triggers for the CMS endcap detectors, efficiency analysis should be done for the other triggers as well Try to calculate the Higgs mass the data obtained from the L1T Acknowledgements Thanks to NSF, Kevin Ingersent, and Alan Dorsey for the REU program Thanks to Prof. Darin Acosta for guiding my research