Can micro channeling improve the TOTEM experimentCan micro channeling improve the TOTEM experiment

Suggestions by V. Avati and K. Eggert

Idea: Crystal placed at 6 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

TOTEM APV hybridFlexible

connections(In production)

detector

beam

ROMAN POT DETECTORS and ELECTRONICSROMAN POT DETECTORS and ELECTRONICS

Readout chip VFAT

Pitch adapter on detector

Test card for VFAT

Detector Distance vs. Beam

nσ-reach?

(RA LHC MAC 13/3/03)

Detector distance vs. beam is determined by the beam halo.

n = dmin/x,y(z) 10-15

Expected halo rate: 6kHz(for 43 bunches, Np = 1010, N = 1m, n = 10)

Active detector starts at the distance from the physical edge

Closest approach :n = 10

= 200m

Elastic Scattering* = 1540 m

acceptance

Example ProcessesExample Processes

2

22 'ppp

P

p1

p2p2’

X d/dproton:p2’ diffractive system Xrapidity gap

=–ln

min 0ln(2pL/pT) max

Measure leading proton ( and rapidity gap ( test gap survival).

Single Diffraction:

2=– ln 1=– ln

p1

p2 p2’

p1’

PMX

2 = s

PX

diffractive system Xproton:p2’proton:p1’

rapidity gaprapidity gap

min max

Double Pomeron Exchange:

Measure leading protons ( 1, 2) and compare with MX, 1, 2

MX2 = s

Diffractive Higgs ProductionDiffractive Higgs Production

MH2 = s

%86.0%86.0

    1202

12

cGeVM Higgs

beam

p’

p’roman pots roman pots

dipoledipole

b -jet

Hgap gap

b -jet

p p

(1-p

(1-p

Roman Pots in the forward regions

Leading diffractive protons seen at different detector locations (* = 0.5m)

y(m

m)

x(mm)

220m

y(m

m)

x(mm)

420m

Dispersion D = 0.08 m D=1.5m

Crystal extraction

RP stations

6 6 x x beam profilebeam profile with crystal extraction with crystal extraction

RP stations

Crystal extraction

Hit distribution in the RP detectorHit distribution in the RP detector

protons deflected by the crystal

the other protons in RP

X [m]

Y [m]

10 beam profile

Detector edge

Angular distribution in the detectorAngular distribution in the detector

= 15rad

Bent by the crystal (by 0.5 mrad)

rad

-acceptance for a Higgs with -acceptance for a Higgs with MMHH=120 GeV/c=120 GeV/c22

In Totem acceptance (68% of 1)

With cristal extraction

2<1

Totem acceptance with cristal extraction (87% of 1)2<1

Conclusions

Crystal extraction is promising to approach the LHC beams Crystal extraction is promising to approach the LHC beams closer than with standard RP detectorscloser than with standard RP detectors

Larger acceptance for diffractively produced HiggsLarger acceptance for diffractively produced Higgs

Same method could be used for elastic scattered protons to Same method could be used for elastic scattered protons to reach the Coulomb regionreach the Coulomb region

Needs extensive tests with crystals and Roman Pots in the Needs extensive tests with crystals and Roman Pots in the SPS (see talk of Marco Oriunno)SPS (see talk of Marco Oriunno)