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Efficiency of the CMS Level-1 Trigger to Selected Physics Channels

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

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Efficiency of the CMS Level-1 Trigger to Selected Physics Channels

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  1. Efficiency of the CMS Level-1 Trigger to Selected Physics Channels by: Corey Sulkko Faculty Mentor: prof. Darin Acosta Funded by: National Science Foundation

  2. 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

  3. 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 ,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

  4. the Large Hadron Collider

  5. 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...

  6. 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

  7. 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

  8. 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

  9. 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

  10. 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

  11. Calculating the Efficiency of the Trigger • run simulations of the collisions, the detectors, and the Trigger • calculate the efficiency

  12. Objectivity Database Objectivity Database ytivitcejbO esabataD Simulating the Experiment Detection Signal Zebra files with HITS Collisions HEPEVT ntuples CMSIM MC Prod. MB Catalog import Objectivity Database ORCA Digitization (merge signal and MB) Objectivity Database ORCA ooHit Formatter ORCA Prod. Triggering Catalog import HLT Algorithms New Reconstructed Objects Objectivity Database HLT Grp Databases Mirrored Db’s (CERN, US, Italy,…)

  13. 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

  14. 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

  15. Results • ROOT was used to calculatethe 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

  16. Efficiency of the L1T to select 1 and 2 muon events as a function of Higgs mass for select Higgs decays

  17. 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

  18. 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

  19. 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

  20. Probability of B -> J/y -> µµgenerating 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%

  21. 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

  22. Acknowledgements • Thanks to NSF, Kevin Ingersent, and Alan Dorsey for the REU program • Thanks to Prof. Darin Acosta for guiding my research

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