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Physics simulation activity for the CMS/TOTEM TDR. Valentina, Fabrizio, Mario, Stefano, Giuseppe, Ken, Mikael, Eric. Outline. Running scenarios Forward proton measurement Acceptance resolution Background rates Trigger for diffraction DPE at low luminosity. Running scenarios. Soft diff.
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Physics simulation activity for the CMS/TOTEM TDR Valentina, Fabrizio, Mario, Stefano, Giuseppe, Ken, Mikael, Eric Fabrizio Ferro
Outline • Running scenarios • Forward proton measurement • Acceptance • resolution • Background rates • Trigger for diffraction • DPE at low luminosity Fabrizio Ferro
Running scenarios Soft diff Hard diff Hard diff Hard diff, rare processes • 1540m: ideal optics for total x-section. Parallel to point focusing. Unfortunately unlikely at the beginning. • 90m: new optics. Likely at beginning (uses standard injection optics). Parallel to point focusing only in the vertical plane (primary vertex position needed). Fabrizio Ferro
Acceptance (RP 220m) DPE events simulated with PHOJET and tracked with MAD 30% acc. contours Fabrizio Ferro
In DPE: measurement: resolution (90m optics) • 220m RP used • x=x(x*,): x from RP, x* from central dets • Mass resolution in DPE depends on lead/Nlead ratio Fabrizio Ferro
measurement: resolution (1540m optics) • Using 145 and 220m RP with D2 in the middle: spectrometer Fabrizio Ferro
*=0.5m, 220m RP Angular selection to reject beam-gas Background in RP • Beam halo: beam p’s lost from design orbit • Beam-gas: shower particles from beam-gas interactions (simulated from upstream TAS to RP): rate < a few 100 Hz • p-p: forward generated particles in p-p inelastic interactions in IP5 Single arm background rates from p-p coll. (preliminary) Fabrizio Ferro
Diffractive trigger at low luminosity Example • Rate constraints: • <1kHz @ L1 • <100Hz on tape for special runs • DPE and SD rates studied • DPE scheme: 2 protons + activity in T1/T2 • SD scheme: 1 proton + activity in T1/T2 opposite side • SD more sensitive to background • For DPE left-right anti-collinearity required • Problem: no detailed info about low-pT (<20GeV) jets available • e~50% for pT>20 GeV and e~100% for pT>50GeV Fabrizio Ferro
Cross section Acceptance DPE at low luminosity • Final physics goals: • Measure central mass • Measure Rapidity Gap survival probability • Measure cross sections ds2/dtdx • Method: • Measure Rap. Gaps with whole TOTEM+CMS • Combine reconstructed directly or indirectly (Rap. Gaps) with the jets reconstructed in CMS • Simulation: two samples: soft DPE (PHOJET) and dijets DPE (DPEMC) Fabrizio Ferro
Gap reconstruction Gap residuals in dijets DPE • Definition: Gap=10-max • max measured with T1, T2 and Ecal (barrel and endcaps) • T1/T2 tracks from full simulation • Calorimetry from FAMOS • Energy deposit >100 MeV in EB and >450 MeV in EF Fabrizio Ferro
reconstruction with gaps Limit of direct measurement • Linear fit of Gap vs log() Generation level Simulation Fabrizio Ferro
Conclusion • Interesting diffractive physics can be done by CMS/TOTEM also in the very first period of LHC operation (the 90m optics seems to be a rather good compromise between an easy-to-do and a good-for-physics optics) • A draft of the work done so far for the PTDR is almost ready • The work is still in progress: • Jet reconstruction difficult without much help from CMS • Rapidity Gap survival: no generator available to estimate how well we can measure the fraction of survived gaps Fabrizio Ferro
