TeV muons: from data handling to new physics phenomena Vladimir Palichik JINR, Dubna NEC’2009 Varna, September 07-14, 2009

I n t r o d u c t i o n This November it is expected to start data taking at the LHC experiments. Multi-purpose physical program at these experiments makes high demands of their detecting systems. The essential part of these physical tasks are the processes with reconstruction of muons. Studies with TeV muons at the CMS experiment can lead to new physical phenomena discoveries and also be a tool for testing of reconstruction algorithms on their efficiency and a precision of measurements.

O u t l i n e cathode strip chamber resolution on cosmic muon data CMS muon reconstruction algorithm in the endcap TeV di-muon events reconstruction in CMS on MC data

 r  ~ 2% of strip width, i.e. ~  for ME1/1 (CMS requirement: <150  )

CSC Spatial Resolution on Muon Cosmic Data Special requirements for resolution calculation: 1) 6 hits on a track segment; 2) cut on large angles of muons: dx/dz < 0.15 dy/dz <1.5; 3) track-segment    criteria. First data ( years) with cosmic muons gave a possibility to verify and adapt specialized software to real data handling (calibrations, algorithms etc.).

ME1/1 single layer spatial resolution on cosmic muon data ME1/1 is the first of CSC chambers in the endcap muon system (full of Dubna JINR responsibility) ME1/1 is located in the most strong magnetic field region in comparison to all other ME stations Thus, ME1/1 plays a key role in reconstruction in the muon endcap system  = 107  m ME1/1 single layer spatial resolution on cosmic data (~110 microns) is agreed with the CMS requirements (< 150 microns) Resolution versus Radius Resolution versus Magnetic Field

Bremsstrahlung and e-m showering close to hard muons lead to the problems with reconstruction in the muon system

Muon Reconstruction Algorithm Local pattern recognition: Local Regional Global (individ.detectors) (Muon system) (Muon & Tracker system) 1.Drift Tubes in the Barrel 2.CSCs in the Endcap: clusters of Digis *) fitted into RecHits, i.e. position of hits in the detector layers. 3.Track-segment building (track following & track road methods) with the compatible RecHits in muon chambers. The track-segments are selected by a goodness of fit criteria (  2 ). *) “Digis” – digitized electronic signals

Regional Muon Reconstruction Standalone Muon system (DT,CSC and RPC): I Y Station 1 Station 3 Station 2 Station 4 e.m.showers& punchthrough Multiple scattering, energy losses, bremsstrahlung, e + e - pair production etc. in Iron Yokes (I Y) Recursive track fitting (from hit to hit in endcap; with use segments in barrel) by the least squares method ( Kalman filter propagation & parameter estimation) HCALHCAL from Hadron Calorimeter (HCAL) Muon trajectory is built on a base of CSC and DT track-segments

Global Muon Reconstruction inclusion of tracker hits starts from standalone reconstructed muons, propagated through calorimeters to outer tracker surface regional track reconstruction is performed using Tracker hits within this (  )- region; to resolve the ambiguities, all the reconstructed tracks are then refitted including the tracks in the muon chambers TeV Muons: In the Tracker hard muons look like straight lines easy to reconstruct but it is impossible to estimate Pt for the straight lines. It is necessary to include hits from the Muon system into the Global reconstruction.

New Physics Phenomena with Heavy Mass di-muons  Signals from physics beyond the Standard Model  Extended gauge models (Z’ bosons)  Randall-Sundrum Gravitons  Virtual graviton production in the model with large extra dimensions  Etc. …  Testing of Standard Model prediction for the Drell-Yan continuum up to TeV energy scale

1 TeV Global Muon Reconstruction in CMS Transverse momentum resolution = 9.4% Efficiency of reconstruction = 99.15% Endcap region 1.2 <  < 2.1 MC data

Di-muon Events Reconstruction in CMS we require at least one muon to be in the endcap  45% of all the Z ’ (2000) events (both muons in 2.4  -region) Z’ (2000 GeV) GeV dM/M = 4.8% Efficiency = 94.3% MC data

S U M M A R Y Cosmic muon data handling Precision of measurements in the muon system (especially in the ME1/1 station) plays a leading role in achieving of the required resolution on transverse momentum and mass reconstruction for the processes with hard muons. ME1/1 single layer spatial resolution obtained on cosmic data (~110 microns) is agreed with the CMS requirements (< 150 microns) Di-muon events in TeV region CMS physical program in particular includes the searching of new TeV- mass resonances in dimuon channel and the testing of Standard Model prediction for the Drell-Yan continuum up to TeV energy scale. Studies of TeV muon processes on simulated data allow to achieve high efficiency and obtain satisfied di-muon mass resolution in the TeV energy region.