1. 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

2. TOTEM ROMAN POT IN CERN SPS BEAM

3. 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

4. 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

5. Elastic Scattering
b* = 1540 m
acceptance

6. 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

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

8. 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)

9. 6 x beam profile with crystal extraction
RP stations
6 x beam profile with crystal extraction
RP stations
Crystal extraction

10. 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

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

12. -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) 

13. 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)