7/6/06 CERN - TOTEM Coll. Meeting Fabrizio Ferro 1

Physics simulation activity for the CMS/TOTEM TDR

Valentina, Fabrizio, Mario, Stefano, Giuseppe, Ken, Mikael, Eric

7/6/06 CERN - TOTEM Coll. Meeting Fabrizio Ferro 2

Outline• Running scenarios

• Forward proton measurement– Acceptance resolution– Background rates

• Trigger for diffraction

• DPE at low luminosity

7/6/06 CERN - TOTEM Coll. Meeting Fabrizio Ferro 3

Running scenarios

* #bunches L

1540 156 2*10^29

90 156 3*10^30

18 936-2808 10^32

<2 936-2808 10^32-10^33

Soft diff

Hard diffHard 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).

7/6/06 CERN - TOTEM Coll. Meeting Fabrizio Ferro 4

Acceptance (RP 220m)

DPE events simulated with PHOJET and tracked with MAD

30% acc. contours

7/6/06 CERN - TOTEM Coll. Meeting Fabrizio Ferro 5

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

sM 21In DPE:

7/6/06 CERN - TOTEM Coll. Meeting Fabrizio Ferro 6

measurement: resolution (1540m optics)

• Using 145 and 220m RP with D2 in the middle: spectrometer

7/6/06 CERN - TOTEM Coll. Meeting Fabrizio Ferro 7

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

*=0.5m, 220m RP Angular selection to reject beam-gas

1540 90 0.5

0.1 – 0.4 kHz 1-4 kHz 1-4 MHz

Single arm background rates from p-p coll. (preliminary)

7/6/06 CERN - TOTEM Coll. Meeting Fabrizio Ferro 8

Diffractive trigger at low luminosityExample• 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

• ~50% for pT>20 GeV and ~100% for pT>50GeV

7/6/06 CERN - TOTEM Coll. Meeting Fabrizio Ferro 9

DPE at low luminosity• Final physics goals:

– Measure central mass – Measure Rapidity Gap survival probability– Measure cross sections d2/dtd

• 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)Cross section Acceptance

7/6/06 CERN - TOTEM Coll. Meeting Fabrizio Ferro 10

Gap reconstruction

• 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

Gap residuals in dijets DPE

7/6/06 CERN - TOTEM Coll. Meeting Fabrizio Ferro 11

reconstruction with gaps• Linear fit of Gap vs log()

Generation level

Simulation

Limit of direct measurement

7/6/06 CERN - TOTEM Coll. Meeting Fabrizio Ferro 12

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

7/6/06 CERN - TOTEM Coll. Meeting Fabrizio Ferro 13

7/6/06 CERN - TOTEM Coll. Meeting Fabrizio Ferro 14

7/6/06 CERN - TOTEM Coll. Meeting Fabrizio Ferro 15