Comparison of trigger efficiencies rates for DT

Comparison of trigger efficiencies & rates for DT, CSC & RPC triggers using W → μν sample Archana Sharma, Suman. B. Beri Panjab University, Chandigarh INDIA

Brief Introduction 3 -dimensional view of CMS detector The detector is specially optimized for muon measurement, so muons chambers are the biggest & most important part of it.

The CMS muon Detectors Location of the muon detectors This is made of : Drift Tubes (DTs) located outside of the magnetic coil in the barrel region. Cathode Strip Chambers (CSCs) in the endcap region. Resistive Plate Chambers (RPCs) lies in both regions. In the barrel the stations are labeled MB 1 -4. The two innermost stations, MB 1 & MB 2 contains two RPC modules & one DT each, whereas stations MB 3 & MB 4 house one RPC & one DT. One RPC module and one CSC are placed in every endcap station (ME 1 -4).

RPC Muon Trigger RPC planes and different tower boundaries used for triggering • RPC based muon trigger for CMS covers the pseudorapidity region |η|<2. 1. • Four RPC planes used for triggering both in barrel & endcap region located in muon stations MB 1 -4 (barrel) & ME 1 -4 (endcap). • Muons with 3

• Solenoidal fields bend the track in rφ plane while η values of trajectory remains almost unchanged. • Pattern of hits recorded by RPCs carries the information about the bending so determine the pt of the track by its comparison with a predefined set of patterns corresponding to a certain pt value. • This device called Pattern Comparator Trigger whose basic logical unit called Segment handled by single PAC processor which is defined by 8 strips in reference muon station. • RE 2 & inner or outer RPC plane in RB 2 is chosen as reference plane.

• Number of strips in non reference planes connected to a single PAC is larger than 8 in order to account for track bending. • Each segment processor is equipped with a Pattern Comparator (PAC) chip which compares patterns of hits from 4 RPC planes with predefined valid patterns. • Assign a maximal pt value from a certain pt range to the muon from pattern produced by it. • The quality assigned to muons after coincidence in different planes is as follows: Quality Low pt algorithm High pt algorithm 3 All planes present 2 Not used Missing plane 3 or 4 1 Not used Missing plane 1 0 One plane missing Missing plane 2

DT Trigger : • Drift Chambers deliver the data for track reconstruction & triggering on different data paths. • The trigger front end device which is directly interfaced to the wire front end electronics is called Bunch & Track identifier (BTI). • BTI performs the bunch crossing assignment of every found muon track segment candidate. • The algorithm used in device can generate false triggers, hence in the bending plane of a system composed by a track corelator (TRACO) & a chamber trigger server (TS) is used to filter the information of the two φ superlayers of a chamber in order to lower the trigger noise. • Track segment found in each station are then transmitted to a regional trigger system called Drift Tube Track Finder which connect the track segment delivered by the stations into a full track & assign a pt value to the finally resolved muon track.

• Memory based look up tables are used to determine pt, φ and η coordinate & track quality. • Each sector processor forwards the two best ranking candidate with the highest pt. • The 4 highest momentum tracks are selected & then forwarded to the Global muon trigger. Block scheme of the local trigger of a drift chamber :

CSC Trigger : Principle of the CSC Local Trigger for Cathode : • CSC local triggers provides high rejection power against all types of backgrounds which are expected from pions, primary muons & neutron induced gamma rays , by finding muon segments in the 6 -layered endcap muon CSC chamber. • Muon segment are first found separately by anode & cathode electronics & then time corelated , providing the precision. • Cathode & anode segments are brought into coincidence and sent to CSC track finder electronics which links the segment from the endcap muon stations.

• CSC muon sorter module selects the four best CSC muon candidate and send them to global muon trigger. • Quality is assigned according to the number of segments used in the track: Three or more segment correspond to quality 3, two segments one of them coming from ME 1, gives quality 2, any two other segments results into quality 1. CSC local trigger for anode :

Preliminary Work Done : • The channel selected for study is W→ μν. • This data sample used for study taken from DBS-2 /Wmunu/CMSSW_1_6_7 -CSA 07 -1192835438/RECO • Steps of generation, simulation & digitization performed in CMS software (CMSSW) in which new geometry of RPC is included in GEANT 4. • Efficiency of the RPC, DT and CSC triggers & statistical error in it is plotted for this sample. • The efficiency of RPC trigger is plotted in different towers corresponding to the different η values to see the variation of trigger efficiency with η.

Efficiency Plots of RPC trigger Efficiency & Error in efficiency pt pt

Efficiency Plots of DT trigger efficiency & Error in efficiency pt pt Efficiency Plots of CSC trigger Efficiency & Error in efficiency pt pt

RPC trigger efficiency in towers corresponding to different η values 0. 06 < |η| < 0. 25 Efficiency |η| < 0. 06 pt pt 0. 41 < |η| < 0. 54 Efficiency 0. 25 < |η| < 0. 41 pt pt

0. 7 < |η| < 0. 83 Efficiency 0. 54 < |η| < 0. 7 pt pt 0. 93 < |η| < 1. 04 Efficiency 0. 83 < |η| < 0. 93 pt pt 1. 14 < |η| < 1. 24 Efficiency 1. 04 < |η| < 1. 14 pt pt

1. 36 < |η| < 1. 48 Efficiency 1. 24 < |η| < 1. 36 pt pt 1. 61 < |η| < 1. 73 Efficiency 1. 48 < |η| < 1. 61 pt pt 1. 85 < |η| < 1. 97 pt 1. 97 < |η| < 2. 1 Efficiency 1. 73 < |η| < 1. 85 pt pt

Summary: On the basis of the distribution it can be shown that the muons from the sample W → μν has low statistics in the pt range above 50 Ge. V. The average efficiency of RPC trigger in both barrel & endcap region is approx. 80% where as average efficiency of DT in barrel & CSC in endcap is approx. 90%. The RPC trigger efficiency in large in towers greater then 10. i. e muons are of high rapidity. The plan of work to be done in continuation of this is as follows: • To apply various pt cuts on the triggered muons & find the optimum pt corresponding to maximum trigger efficiency. • Comparison of the trigger efficiencies of DT & RPC in barrel and CSC & RPC in end-cap region. (could not be completed because of CASTER problem from the last few days) • To study the physics aspects of the channel W→ μν. *This work is being done with RPC, DPG & trigger groups at CERN