Can micro channeling improve the TOTEM experiment Suggestions by V. Avati and K. Eggert Idea: Crystal placed at 6 s from the LHC beam, deflecting the protons, can improve considerably the proton acceptance of the TOTEM Roman pots Principle lay-out Physics example: Higgs search in central diffraction Crystal Collimation in Hadron Storage Rings, CERN 7-8 March 2005

TOTEM ROMAN POT IN CERN SPS BEAM

ROMAN POT DETECTORS and ELECTRONICS TOTEM APV hybrid Flexible connections (In production) beam Readout chip VFAT detector Pitch adapter on detector Test card for VFAT

Detector Distance vs. Beam Detector distance vs. beam is determined by the beam halo. nσ-reach? (RA LHC MAC 13/3/03) ns = dmin/sx,y(z)  10-15 Expected halo rate: 6kHz (for 43 bunches, Np = 1010, eN = 1mm, ns = 10) Active detector starts at the distance d from the physical edge Closest approach : ns = 10 d = 200mm

Elastic Scattering b* = 1540 m acceptance

Double Pomeron Exchange: Example Processes Single Diffraction: X p1 ds/dh proton:p2’ MX2 = x s diffractive system X rapidity gap P Dh =–ln p2’ hmin hmax p2 ln(2pL/pT) Measure leading proton ( x) and rapidity gap ( test gap survival). Double Pomeron Exchange: p1 p2 p2’ p1’ P diffractive system X proton:p2’ proton:p1’ rapidity gap hmin hmax X MX2 = x1 x2 s P Dh2=– ln x2 Dh1=– ln x1 Measure leading protons ( x1, x2) and compare with MX, Dh1, Dh2

Diffractive Higgs Production -jet H gap h p (1-x2)p (1-x1)p MH2 = x1x2 s beam p’ roman pots dipole

Roman Pots in the forward regions y(mm) x(mm) 220m y(mm) x(mm) 420m Dispersion D = 0.08 m D=1.5m x Leading diffractive protons seen at different detector locations (b* = 0.5m)

6 x beam profile with crystal extraction RP stations 6 x beam profile with crystal extraction RP stations Crystal extraction

Hit distribution in the RP detector protons deflected by the crystal the other protons in RP X [m] Y [m] 10 s beam profile Detector edge

Angular distribution in the detector  = 15rad Bent by the crystal (by 0.5 mrad) rad

-acceptance for a Higgs with MH=120 GeV/c2 In Totem acceptance (68% of 1) With cristal extraction 2<1 Totem acceptance with cristal extraction (87% of 1) 

Conclusions Crystal extraction is promising to approach the LHC beams closer than with standard RP detectors Larger acceptance for diffractively produced Higgs Same method could be used for elastic scattered protons to reach the Coulomb region Needs extensive tests with crystals and Roman Pots in the SPS (see talk of Marco Oriunno)