TOTEM Physics

1

• TOTEM Physics
• s tot
• elastic scattering
• diffraction (together with CMS)

Karsten Eggert CERN, PH Department on behalf of
the TOTEM Collaboration http//totem.web.cern.ch/T
otem/
TOTEM TDR is fully approved by the LHCC and the
Research Board
XI th Int. Conf. on Elastic and Diffractive
Scattering, Blois, France, May 2005
2
TOTEM Physics
Total cross-section with a precision of
1 Elastic pp scattering in the range 10 -3 lt
t (p ? )2 lt 10 GeV2 Particle and energy flow
in the forward direction Measurement of leading
particles Diffractive phenomena with high
cross-sections
Different running scenarios (b 1540, 170, 18,
0.5 m)
3
Total p-p Cross-Section

• Current models predict for
• 14 TeV 90 130 mb
• Aim of TOTEM 1 accuracy
• Luminosity independent method

COMPETE Collaboration fits all available hadronic
data and predicts at LHC
PRL 89 201801 (2002)
4
Experimental apparatus
5
T1 and T2 Telescopes
(see talk of G. Ruggiero)
2004 Test Beam in X5
T1 Cathode Strip Chambers
400 mm
ltIP5
6
Roman Pot station with two units 4 m apart
BPM
Roman Pot unit -Vertical and horizontal pots
mounted as close as possible -BPM fixed to the
structure gives precise position of the
beam -Final prototype at the end of 2005
7
Edgeless Silicon Detectors for the RPs
Planar technology Testbeam
40 ?m dead area
66 mm pitch
50 mm dead area
10 mm dead area
active edges (planar/3D)
planar technology CTS (Curr. Termin. Struct.)
8
Running Scenarios
9

• TOTEM Optics Conditions

LTOTEM 1028 cm-2 s 1
TOTEM needs special/independent short runs at
high-b (1540m) and low e Scattering angles of a
few mrad
High-b optics for precise measurement of the
scattering angle s(q) ?e / b 0.3
mrad As a consequence large beam size
s ? e b
0.4 mm Reduced number of bunches ( 43 and 156
) to avoid interactions further downstream
Parallel-to-point focusing ( v0) Trajectories
of proton scattered at the same angle but at
different vertex locations
y Ly qy vy y L (bb)1/2
sin m(s) x Lx qx vx xx Dx v
(b/b)1/2 cos m(s)
Maximize L and minimize v
10
High b optics ( 1540 m ) lattice functions
v (b/b)1/2 cos m(s) L (bb)1/2 sin m(s)
L (m)
Parallel to point focusing in both projections
v
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Elastic Scattering
b 1540 m
acceptance
12
Elastic Scattering Resolution
f-resolution (1-arm measurement)
t-resolution (2-arm measurement)
Test collinearity of particles in the 2 arms ?
Background reduction. f correlation in DPE
13
Elastic Cross section (t0)
tmax 0.1 GeV2
14
Extrapolation uncertainty due to Coulomb
interference
Extrapolation to t0 model dependent
Error lt 0.5
ds/dt exp( -Bt)
Coulomb interference
Change of the slope B
15
Accuracy of s tot (sinel.80mb, sel.30mb)
1
Trigger Losses (mb)
Vertex extrapolation
simulated
extrapolated
Acceptance
detected
16
Possibilities of r measurement

• Try to reach the Coulomb region and measure
  interference
• move the detectors closer to the beam than 10 ?
  0.5 mm
• run at lower energy vs lt 14 TeV

17
Elastic Scattering Cross-Section
Photon - Pomeron interference ? r
ds/dt mb / GeV2
Multigluon (Pomeron) exchange ? e B t
104 per bin of 10-3 GeV2
diffractive structure
? t ? p2 q2
pQCD
wide range of predictions
pp 14 TeV BSW model
-t GeV2
b18 m L 3.6 x 1032 cm-2 s-1 (2)
b 1540 m L 1.6 x 1028 cm-2 s-1 (1)
1 day (1) (2)
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CMS TOTEM Acceptance
CMSTOTEM largest acceptance detector ever built
at a hadron collider
gt 90 of all diffractive protons are detected 10
million min. bias events, including all
diffractive processes, in a 1 day run with b
1540 m
Charged particles
dNch/dh
dE/dh
Energy flux
b172m (prelim.)
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• CMS/TOTEM Physics
• CMS / TOTEM detector ideal for study of
  diffractive and forward physics
• Soft and hard diffraction in Single and Double
  Pomeron Exchange
• production of jets, W, J/y, heavy flavours, hard
  photons
• Excellent proton measurement gap survival
• Double Pomeron exchange as a gluon factory
• Production of low mass systems (SUSY, c
  ,D-Y,jet-jet, )
• Glue balls,
• Higgs production ???
• Structure functions (parton saturation) with and
  without detected protons
• Forward physics DCC, particle and energy flow
• gg physics

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TOTEMCMS Physics Diffractive Events
Measure gt 90 of leading protons with RPs and
diffractive system X with T1, T2 and CMS.
-Triggered by leading proton and seen in
CMS -Central production of states X X cc, cb,
Higgs, dijets, SUSY particles, ...
21
Running Scenarios
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Diffractive protons at ?1540 m
Diffractive protons are observed in a large ?-t
range gt 90 are detected -t gt 2.5 10 -3
GeV2 10-8 lt ? lt 0.1 ? resolution few
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(mm)
(mm)
mm
Diffractive proton detection at b 0.5 m ??gt
2.5
(mm)
(mm)
log ?
log ?
log -t
log -t
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New optics b172 m
To optimize diffractive proton detection at
L1032 in the warm region at 220m

• Ly large (270 m)

tmin 2 x 10-2 GeV2
10? beam

• Vertex measured by CMS

65 of all diffractive protons
are seen
x determination with a precision
of few 10 -4
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Diffractive protons at b172 m
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Conclusion on new optics (b172 m) - preliminary

• Luminosity of 0.5 x 1032 cm-2 s-1
• About 65 of diffractive protons are seen in the
  RP at 220 m
• x resolution of 4 10 -4
• q resolution of few mrad
• Future
• more detailed studies on resolution
• further optimization towards higher luminosities

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Example Processes
Single Diffraction
X
ds/dh
p1
protonp2
MX2 x s
diffractive system X
rapidity gap
P
Dh ln?
hmin
0
hmax
p2
ln(2pL/pT)
p2
Measure leading proton (? x) and rapidity gap (?
test gap survival).
Double Pomeron Exchange
MX2 x1 x2 s
X
P
Dh2 ln x2
Dh1 ln x1
Measure leading protons (? x1, x2) and compare
with MX, Dh1, Dh2
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Exclusive Central Diffraction
The Pomeron has the internal quantum numbers of
vacuum.
Signature 2 Leading Protons 2 Rapidity Gaps
p1
p1

• PP C , I0,...
• P JP 0, 2, 4,...
• PP JPC 0

P
P
Large mass objects O(1TeV) ?c 10 6-7 events
before decay ?b 10 3-4 events before decay - a
precursor to DPE Higgs, SUSY
p2
p2
2p
Gap
Gap
JetJet
?
0
diffractive system
protonp1
h
protonp2
hmin
hmax
rapidity gap
rapidity gap
hmin
hmax
Exclusive physics ? Gluon factory ? Threshold
scan for New Physics
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Exclusive Production by DPE Examples
Advantage Selection rules JP 0, 2, 4 C
1 ? reduced background, determination of
quantum numbers. Good f resolution in TOTEM
determine parity P (-1)J1 ? ds/df 1 cos
2f

• Higgs needs L 1033 cm-2 s-1, i.e. a running
  scenario for b 0.5 m
• try to modify optics locally,
• try to move detectors closer to the beam,
• install additional Roman Pots in cold LHC region
  at a later stage.

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Detection Prospects for Double Pomeron Events
b 1540 m ?? 0.5 L ? 2.4 x 1029
cm-2 s-1 b 172 m ?? 0.2 - 0.4
L 0.5 1032 cm-2 s-1 b 0.5 m
?? 0.2-0.6 L 1033 cm-2 s-1
p1
p1
P
M2 x1 x2 s
Trigger via Roman Pots x gt 2.5 x 10-2 Trigger via
rapidity gap x lt 2.5 x 10-2
P
p2
p2
b 0.5 m
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? and t distributions for 120 GeV Higgs
input
ExHume
Proton acceptance 68
Detected protons at 220 m
log ?
log -t
Phojet
Proton acceptance 63
log -t
log ?
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Mass Acceptance in DPE (preliminary)
?0.5 m
Totem Preliminary
?172 m
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Mass resolution at 420 m and 420220m
Note beam position accuracy 10 ?m
420m PHOJET
Asym. 420215 m
420m EXHUME
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DPE cross-sections
?L dt 40 nb-1 3days
??1540 m
?L dt 10 pb-1 3days
??172 m

• ??c0 3?b x BR(10-3) 3 nb
• ??b0 4nb x BR(10-3) 4 pb
• pp pXp 0.1 - 1 mb
• pp p j1 j2 p
• ptjet gt10 GeV inclusive 1 ?b
• exclusive 7 nb
• jet-jet background to the Higgs
• pp p j1 j2 p
• M(j1 j2) 120 GeV
• exclusive 18 pb / ?M 10 GeV
• (Eur. Phys. J.C25,391)

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Conclusions

• Measure total cross-section stot with a
  precision of 1
• L 1028 cm-2 s-1 with b 1540 m
• Measure elastic scattering in the range 10 -3 lt t
  lt 8 GeV 2
• With the same data study of soft diffraction and
  forward physics
• 107 single diffractive events
• 106 double Pomeron events
• With b 1540 m optics at L 2 ? 1029 cm-2 s-1
  
• semi-hard diffraction (pT gt 10 GeV)
• With b 170 m optics (under study) at L 0.5
  1032 cm-2 s-1
• hard diffraction and DPE
• Study of rare events (Higgs, Supersymmetry,)
  with b 0.5 m
• using eventually detectors in the cold region
  (420m)
• TOTEM and CMS will write a common physics LOI in
  2005

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Diffraction
Example
Exchange of colour singlets (Pomerons) ?
rapidity gaps Dh Most cases leading proton(s)
with momentum loss Dp / p ? x
p
p
Dh1
P
P
Dh2
p
p
Unlike minimum bias events
p
Exchange of colour triplets or octets Gaps
filled by colour exchange in hadronisation ?
Exponential suppression of rapidity gaps
g, q
g, q
P(Dh) e-r Dh, r dn/dh
p
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T1 3.1 lt h lt 4.7 T2 5.3 lt h lt 6.5
Optical Theorem
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Determination of the emission angle via the
measurement at RP-147 m
q precision few mrad
x (147 m)
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Measurement of ?tot
Measurement of the total cross section with the
luminosity independent method using the Optical
Theorem.
Measurement of the elastic and inelastic rate
with a precision better than 1.
42
Particle elongation (x) for Lx0 and different
x-values
Lx
?
? Lx0
Example at x0.007 and different emission angles
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??172 m ? resolution 4 10-4 (preliminary)
? 10-3
2 10-3
X220-x216 (mm)
2?
2?
TOTEM Preliminary
(x220x216)/2 (mm)
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Detector Layout
215m
300m
420m
y(mm)
y(mm)
y(mm)
x(mm)
x(mm)
x(mm)
Dispersion D 0.08 m
D0.7m
D1.5m
Leading diffractive protons seen at different
detector locations (b 0.5m)