TOTEM Physics Scenarios at the LHC;

1
TOTEM Physics Scenarios at the LHC
Elastic Scattering, Total Cross section,
Diffraction, and beyond ...
Risto Orava Helsinki Institute of
Physics and
University of Helsinki
LOW X MEETING
SINAIA, ROMANIA

June 29 - July
2 - 2005
2
CMS is TOTEMized...
Leading Protons measured at -220m -147m from
the CMS
CMS Experimental Area (IP5)
(Also CMS is here...)
TOTEM Experiment

• Leading protons are detected at ?147m ?220m
  from the IP.
• CMS coverage is extended by Totem T1 and T2
  spectrometers.
• Additional forward calorimetry veto counters
  are under planning.

Leading Protons measured at 147m 220m from
the CMS
3
Base Line LHC Experiments pT-h coverage
LHC TOTEMized
Exp B (T) pT? (GeV)
ALICE 0.2-0.5 0.1-0.25
ATLAS 2.0 0.5
CMS 4.0 0.75
LHCb 4Tm 0.1
1000
CMS
ATLAS
100
T1
T1
pT (GeV)
ALICE
LHCb
10
T2
T2
1
microstation
microstation
RP
RP
0.1
veto
veto
pTmax ?s exp(-h)
0
-12
-10
-8
-6
-4
-2
2
4
6
8
10
12
h
The base line LHC experiments will cover the
central rapidity region - TOTEM?CMS will
complement the coverage in the forward region.
4
Base Line LHC Experiments

• ATLAS CMS
• Energy flow in h? 5
• Minimum bias event structure
• need to sort out the pile-up events at L 1033
• present MC models differ by large factors
• ALICE
• Charged multiplicities in -5 ? h ? 3
• Zero Degree Calorimetry (neutral charged)
• TOTEM
• Charged multiplicities 3 ? h ? 7
• Leading particle measurement
• Totem sees all diffractively scattered protons
• TOTEM/CMS inelastic coverage is unique
• Holes only at h 5 7-9 (could be covered
  with ms veto counters)

5
Diffractive scattering is a unique laboratory
of confinement QCD A hard scale hadrons
which remain intact in the scattering process.
Transversal view
Elastic
soft SDE
hard SDE
hard CD
soft CD
Longitudinal view - Lorentz contracted not to
scale!
wee parton cloud - grows logarithmically
p
jet
lnMX2
Baryonic charge distribution-r ? 0.5fm
jet

b
b
h
lns
Valence quarks in a bag with r ? 0.1fm
rapidity

• Soft diffractive scattering
• large b

Hard diffractive scattering - small b
p
Rapidity gap survival underlying event
structures are intimately connected with a
geometrical view of the scattering - eikonal
approach!
10mb?
25mb?
1mb?
Hard processes Jet momenta correlated with the
initial parton momenta.

• Soft processes
• Coherent
• interactions
• impact parameter
• picture.

Cross sections are large.
Totem sees SDE MX ? 20 GeV
6
A Light Higgs Boson as a Benchmark
Recent Tevatron Top-mass measurement
reinforces the motivation.
The new result (using 173.5 ? 4.1 GeV/CDF)
Central preferred value of the Standard Model
Higgs boson mass is 94 GeV, with 68
uncertainties of 54 and -35 GeV. 95 C.L is lt
208 GeV Thanks to Martin Grunewald
7
Central Diffraction produces two leading
protons, two rapidity gaps and a central
hadronic system. In the exclusive process,
the background is suppressed and the central
system has selected quantum numbers.
JPC 0 (2, 4,...)
MX2??1?2s
Measure the parity P (-1)J ds/d? ? 1 cos2?
2p
Gap
Gap
JetJet
?
0
h
hmin
hmax
Mass resolution ? S/B-ratio
Survival of the rapidity gaps?1
see DKMOR EPJC25(2002)391
8
With the leading protons and additional forward
coverage a new physics realm opens up at the
LHC
Elastic scattering, stot and soft diffraction
surely... But also

• Hard diffraction with multi- rapidity gap events
  (see Hera, Tevatron, RHIC...)
• ? Problems intimately related to
  confinement.
• Gluon density at small xBj (10-6 10-7) hot
  spots of glue in vacuum?
• Gap survival dynamics, proton parton
  configurations (pp?3jetsp) underlying event
  structures
• Diffractive structure Production of jets, W,
  J/?, b, t, hard photons,
• Parton saturation, BFKL dynamics, proton
  structure, multi-parton scattering
• Studies with pure gluon jets gg/qq ? LHC as a
  gluon factory! (see KMR EPJC19(2001)477)
• Signals of new physics based on forward protons
  rapidity gaps
• ? Threshold scan for JPC 0 states in
  pp ? pXp
• Spin-parity of X ! (LHC as the pre -ee-
  linear collider in the gg-mode.)
• Extend standard physics reach of the CMS
  experiment into the forward region
• ? Full Monty!
• Measure the Luminosity with the precision of
  DL/L? 5 (KMRO EPJC19(2001)313)

9
As a Gluon Factory LHC could deliver...

• High purity (q/g 1/3000) gluon jets with ET gt
  50 GeV
• gg-events as Pomeron-Pomeron luminosity
  monitor
• Possible new resonant states in a background
  free environment (bb, WW-
• tt- decays) (see KMR EPJC23(2002)311)
• Higgs
• glueballs
• quarkonia 0 (?b )
• gluinoballs
• invisible decay modes of Higgs (and SUSY)!?
• CP-odd Higgs
• Squark gluino thresholds are well separated
• practically background free signature
  multi-jets ET
• model independence (missing mass!) expect O(10)
  events for gluino/squark masses of 250 GeV
• an interesting scenario gluino as the LSP with
  mass window 25-35 GeV(S.Raby)
• Events with isolated high mass gg pairs

-
10
Low-x Physics at the LHCResolving Confinement of
quarks gluons?
The forward detectors at the LHC will facilitate
studies of collisions between transversally
extended slices of QCD vacua with quantum
fluctuations?
J. Stirling
11
Probing Very Small-x Gluons

• Consider a high momentum proton
• Measure gluon distribution G(x,Q2) at fixed Q2
• and small x with xQ
• ? probe gluons with the transverse size
  Db1/Q and
• longitudinal size Dz1/px.
• gluon saturation, colour-glass condensates,
• colour-dipoles,....

In SD If a pair of high ET jets are produced,
then If the interacting partons have
fractional momenta b of P, then bxBj/?, then (if
all hadrons i in the event are measured)
Instrument region with
tracking, calorimetry (emhad), muons, jets,
photons ...
12
LHC due to the high energy can reach small
values of Bjorken-x If rapidities above 5 and
masses below 10 GeV can be covered ? x down to
10-6 10-7 Possible with T2 in TOTEM
(calorimeter, tracker) 5 lt ? lt 6.7
Proton structure at low-x Parton saturation
effects?
Saturation or growing proton?
13
Puzzles in High Energy Cosmic Rays
Cosmic ray showers Dynamics of the high energy
particle spectrum is crucial
Interpreting cosmic ray data depends on hadronic
simulation programs. Forward region in poorly
known. Models differ by factor 2 or more. Need
forward particle/energy measurements e.g.
dE/d?
PYTHIA PHOJET ExHuME...??
14
Chuck Dermer (BNL)
15
The Underlying Event Problem inHard Scattering
Processes
Min-Bias
Min-Bias

• LHC most of collisions are soft, outgoing
  particles roughly in the same direction as the
  initial protons.
• Occasional hard interaction results in
  outgoing partons of large transverse momenta.
• The Underlying Event is everything but the two
  outgoing Jets, including
• initial/final gluon radiation
• beam-beam remnants
• secondary semi-hard interactions
  

• Unavoidable background to be removed from the
  jets before comparing to NLO QCD predictions

This is already of major importance at the
Tevatron how about the LHC??
16
In addition The signatures of New Physics have
to be normalized ? Measure the Luminosity
Luminosity relates the number of events per
second, dN/dt, and the cross section of process
p, sp, as
A process with well known, calculable and large
sp (monitoring!) with a well defined signature?
Need complementarity.
Measure simultaneously elastic (Nel) inelastic
rates (Ninel), extrapolate ds/dt ? 0, assume
r-parameter to be known
(1r2) (Nel Ninel)2
L
16p dNel/dtt0
Ninel ? ? Need a hermetic detector. dNel/dt?
t0 ? ? Minimal extrapolation to t?0 tmin ?
0.01
see KMOR EPJ C23(2002)
17
Signatures

• Proton (Roman Pots)
• elastic proton (b1540m 5 ? 10-4 ? -t ? 1
  GeV2, b18m 3?10-1 ? -t ? 10 GeV2)
• diffractive proton (b1540m 90 of all
  diffractive protons ? ? 10-2 -t ? 10-3 GeV2)
• hard diffractive proton (b 0.5m excellent
  coverage in ?-t space)
• Rapidity Gap (T1 T2, Castor ZDC)
• rapidity gaps (up to L 1033cm-2 s-1 3 ? h?
  7, veto counters?)
• Very Fwd Objects (T1 T2, Castor ZDC)
• Jets (up to L 1033cm-2 s-1 3 ? h? 7, veto
  counters?)
• g, e, m (fwd em calorimetry muons 3 ? h? 7)
• tracks (vx constraints pattern recognition 3
  ? h? 7)
• particle ID?
• Correlation with CMS Signatures (central jets,
  b-tags,...)

18
Correlation with the CMS Signatures

• e, g, m, t, and b-jets
• tracking h lt 2.5
• calorimetry with fine granularity h lt 2.5
• muon h lt 2.5
• Jets, ETmiss
• calorimetry extension h lt 5
• High pT Objects
• Higgs, SUSY,...
• Precision physics (cross sections...)
• energy scale e m 0.1, jets 1
• absolute luminosity vs. parton-parton luminosity
  via
• well known processes such as W/Z production?

19
Configuration of the Experiment
Aim at detecting colour singlet exchange
processes with the leading protons scattered at
small angles with respect to the beam.
b-jet
Roman Pot Station at 147 / 220m
Roman Pot Station at 147/220m
CMS
T1
CASTOR
T1
T2
T2
CASTOR
-
b-jet
Aim at measuring the

• Leading protons on both sides down to D? ? 1
• - Rapidity gaps on both sides forward activity
  for h gt 5
• Central activity in CMS

20
To Reach the Forward Physics Goals
Need

• Leading Protons
• Extended Coverage of Inelastic Activity
• CMS

21
Leading Protons Transfer Functions
To be detected, the leading protons have to
deviate sufficiently from the nominal LHC beams
? special LHC optics detector locations for
elastically scattered protons.

• The proton trajectory, in the plane transverse
  with respect to the beam, at position s
• along the beam line, is given as

- the initial transverse position and scattering
angle at the IP

• the effective length, bx,y(s) value of the
  b-function
• along the beam line, b bx(s0) by(s0) at
  the IP.

- betatron phase advance
- dispersion
- magnification
22
Leading Protons - Measurement
The small-angle protons are detected within the
LHC beam pipe at large distances from the IP. To
facilitate detection of elastically and
diffractively scattered protons, special machine
optics are needed ? b 1540m (-t down to ? 10-3
GeV2), 18m (-t up to ?10 GeV2) For hard
diffraction and low-x physics, nominal high
luminosity conditions are required ? b 0.5m
RP2
RP1
RP3
CMS
147 m
180 m
220 m
RPi Special insertion devices needed for
placing the proton detectors within the beam
pipe ? Roman Pots
IP5 CMS Interaction Point TAS Beam Absorber for
secondaries between the IP and Q1 Qi
Quadrupole Magnets TASA Beam Absorber for
secondaries between Q1 and Q2 TASB Beam Absorber
for secondaries between Q2 and Q3 DFBx Cryogenic
Electrical Feed-Boxfor Arc Di Dipole Magnet
i TAN Beam Absorber for neutral secondaries
before Q1-Q3 BSR Synchrotron Radiation
Observation System TCL Long Collimator for
protecting Quadrupole Magnets
23
Leading Proton Detection-An Example
147m
180m
220m
0m
308m
338m
420 430m
D2
Q4
Q5
Q6
Q7
B8
Q8
B9
Q9
B10
B11
Q10
IP
?
?
?
D1
?
?
?
Q1-3
?
?
?
?
?
x 0.02
?
?
Note the magnification x vs. z!
Helsinki group Jerry Lamsa RO
24
Elastic Protons
For detecting the low t elastic protons down to
t ? 10-3 GeV2 (scattering angles of a few mrad)
need to maximise Lx(ssRPi), Ly(ssRPi) at each
RPi, and, simultaneously, to minimise vx(ssRPi),
vy(ssRPi) at each RPi.
Aim at parallel-to-point focussing condition
vx,y 0 in both x- and y-directions at s220m ?
independence of the initial transverse position
of the IP.
y
? High-b optics b 1540 m
IP
Leff
? low angular spread at IP ? large beam size
at IP
(if eN 1 mm rad)
Reduce number of bunches (43 and 156) to avoid
parasitic interactions downstream.
LTOTEM 1.6 x 1028 cm-2 s-1 and 2.4 x 1029
cm-2 s-1
25
Elastic Scattering ds/dt
ds/dt (mb/GeV2)
-t (GeV2)
26
Elastic Scattering Acceptance in -t
Region t GeV2 Running Scenario
Coulomb region ? 5?10-4 lower s, RP closer to
beam Interference, r meas. 5?10-4 ? 5?10-3 as
above, standard b 1540 m Pomeron exchange
5?10-3 ? 0.1 b 1540 m Diffractive
structure 0.1 ? 1 b 1540 m, 18 m Large t
perturb. QCD 1 ? 10 b 18 m
27
Elastic Scattering Resolution
t-resolution (2-arm measurement)
f-resolution (1-arm measurement)
Test collinearity of particles in the 2 arms ?
Background reduction.
28
Extrapolation of Elastic Cross-Section to t 0
Effect Extrapolation uncertainty
Statistics (10h _at_ 1028) 107 events 0.07
Uncertain functional form of ds/dt 0.5
Beam energy uncertainty 0.05 0.1
Beam / detector offset 20 mm 0.08
Crossing angle 0.2 mrad 0.1
Total 0.53
Non-exponential ds/dt fitted to Slope
parameter according to BSW Model
see KMRO EPJ(2001)313
29
Soft Diffraction (high b) Acceptance
b 1540 m
A gt 95
85 - 95
A lt 5
90 of all diffractive protons are seen in the
Roman Pots -assuming
x Dp/p can be measured with a resolution of
5 x 10-3 .
30
Hard Diffraction (high b) Acceptance
31
Extension to Inelastic Coverage
To measure the colour singlet exchange, need to
extend central detector coverage in the forward
direction h gt 5.
T1 3.1 lt h lt 4.7 T2 5.3 lt h lt 6.5
10.5 m
T1
10.5 m
T2
CASTOR
14 m
32
(No Transcript)
33
Total pp Cross-Section

• Current models predictions 100-130mb
• Aim of TOTEM 1 accuracy

Cosmic Rays
COMPETE Collaboration fits
UA5
TEVATRON
LHC
UA4
ISR
PRL 89 201801 (2002)
LHC
34
Measurement of ?tot

• Luminosity-independent measurement of the total
  cross-section by using the Optical Theorem

• Measure the elastic and inelastic rate with a
  precision better than 1.
• Extrapolate the elastic cross-section to t 0.
• Or conversely
• Extract luminosity

35
Measurement of the Total Rate Nel Ninel
s mb T1/T2 double arm trigger loss mb T1/T2 single arm trigger loss mb Uncertainty after extrapolation mb
Minimum bias 58 0.3 0.06 0.06
Single diffractive 14 - 2.5 0.6
Double diffractive 7 2.8 0.3 0.1
Double Pomeron 1 0.2 (using leading p and CMS) 0.2 (using leading p and CMS) 0.02
Elastic Scattering 30 - - 0.15
Total 0.8
Extrapolation of diffractive cross-section to
large 1/M2 using ds/dM2 1/M2 .
36
Accuracy of stot
Total rate Nel Ninel
r 0.12 0.02
Extrapolation to t 0
37
Total Cross Section - TOTEM
TOTEM
38
Elastic Scattering- TOTEM
TOTEM
39
Running Scenarios
Scenario (goal) 1 low t elastic, stot , min. bias 2 diffractive physics, large pT phenomena 2 diffractive physics, large pT phenomena 3 intermediate t, hard diffraction 4 large t elastic
b m 1540 1540 1540 200 - 400 18
N of bunches 43 156 156 936 2808
Half crossing angle mrad 0 0 0 100 - 200 160
Transv. norm. emitt. mm rad 1 1 3.75 3.75 3.75
N of part. per bunch 0.3 x 1011 0.6 x 1011 1.15 x 1011 1.15 x 1011 1.15 x 1011
RMS beam size at IP mm 454 454 880 317 - 448 95
RMS beam diverg. mrad 0.29 0.29 0.57 1.6 - 1.1 5.28
Peak luminosity cm-2 s-1 1.6 x 1028 2.4 x 1029 2.4 x 1029 (1 - 0.5) x 1031 3.6 x 1032
Runs at b 0.5 m, L (1033 ? 1034) cm-2 s-1
foreseen as an extension to the TOTEM program.
40
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
Particle sexcl Decay channel BR Rate at 2x1029 cm-2 s-1 Rate at 1031 cm-2 s-1
(no acceptance / analysis cuts) (no acceptance / analysis cuts)
?c0 (3.4 GeV) 3 mb KMRS g J/y ? g mm p p K K 6 x 10-4 0.018 1.5 / h 46 / h 62 / h 1900 / h
?b0 (9.9 GeV) 4 nb KMRS g U ? g mm 10-3 0.07 / d 3 / d
H (120 GeV) 3 fb (?2.5fb) bb 0.68 0.02 / y 1 / y

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

41
Hard Diffraction Leading Protons at Low b
horizontal offset ??Dx (? momentum loss)
For a 2.5 mm offset of a ? ? 0.5 proton, need
dispersion ? 0.5 m. ? Proton taggers to be
located at gt 250 m from the IP (i.e. in a
cryogenic section of the LHC).
Dx
?y
Optical function ? in x and y (m)
Dispersion in horizontal plane (m)
?x
CMS
42
Potential locations for measuring the leading
protons in pp ? p ? X ? p with MX O(100
GeV).
Cryogenic (cold) region (with main dipole
magnets)
locations of currently planned TOTEM pots!!
420 m
220 m
CMS
(308/338m)
Dispersion suppressor
Matching section
Separation dipoles
Final focus
43
The TOTEM Detector Layout
220m
300m
420m
2-12mm
y(mm)
y(mm)
1,5-20mm
3,5-17mm
y(mm)
x(mm)
x(mm)
x(mm)
Leading diffractive protons seen at different
detector locations (b 0.5m)
44
Exciting new physics potential in the
process pp ? p ? (JPC0) ? p

• Colour singlet exchange process with exclusive
  priviledges
• - JPC selection rule
• ? ee- ILC type threshold scan for new physics!

h
p
10
p
p
Dh
5
b-jet
P
b
-
0
b
P
-
b-jet
p
p
-5
Dh
-10
p

• Need to solve the L1 trigger issue at high
  luminosity (pile-up)
• conditions.

see KMR EPJ(2002)
45
CD ExHuME (MH 120 GeV)
dN/dhHiggs
hHiggs
46
Event Characteristics ds/dt xmin
x acceptance?
-t lt 1 GeV2
CD PHOJET (MH 120 GeV)
CD PHOJET (MH 120 GeV)
dN/dxmin
dN/dt
-t (GeV2)
xmin
SN/dt
SN/dxmin
-t (GeV2)
xmin
? dN/dt ? exp(-10t)
? should detect ps down to x ? 10-3
47
CD ExHuME (MH 120 GeV)
dN/d?min
?min
0.0 0.001 0.002 0.003 0.004 0.005
0.006 0.007 0.008 0.009 0.010
SdN/d?min
?min
0.0 0.001 0.002 0.003 0.004 0.005
0.006 0.007 0.008 0.009 0.010
48
Where do the b-jets go?
xpmax ? 0.02
xpmin ? 0.002
dN/dhbmax
PHOJET
PHOJET
ExHuME
ExHuME
hbmax
hbmax

• The b-jets are confined within ?h?? 4.
• ExHuME generates more symmetric jet pairs.

49
Leading protons Hard CentralDiffraction

• pp ? p X p simulated using PHOJET1.12
  ExHuME
• Protons tracked through LHC6.2 6.5 optics using
  MAD

• Uncertainties included in the study
• Initial conditions at the interaction point
• Conditions at detector location

• Transverse vertex position (?x,y 11 ?m)
• Beam energy spread (?E 10-4)
• Beam divergence (?? 30 ?rad)

• Position resolution of detector (?x,y 10 ?m)
• Resolution of beam position determination (?x,y
  5 ?m)
• Off-sets at detector locations

J.Lamsa, T. Maki, R.Orava, K.Osterberg...
50
Acceptance ExHuME vs. PHOJET
60
ExHuME 420220m
PHOJET 420215m
38
420m220m ExHuME 420m ExHuME 420m220m
PHOJET 420m PHOJET
22
ExHuME 420m
12
PHOJET 420m
Helsinki group Jerry Lamsa et. al.
"420220" calculation either both protons are
detected at 420m, or both protons are detected at
220m, or one proton is detected at 420 220m
with the other one detected at 220 420m.
51
Resolution ExHuME vs. PHOJET
420m220m ExHuME 420m ExHuME 420m220m
PHOJET 420m PHOJET
PHOJET 420220m
3.7
ExHuME 420220m
2.8
PHOJET 420m
ExHuME 420m
0.9
Helsinki group Jerry Lamsa et. al.
Helsinki group J.Lamsa (parametrisations of the
MAD simulation results of T. Mäki by RO)
52
Rapidity Gap Veto Detector Lay-Out
veto counters
D1
Q1
Q2
Q3
60m
140m
IP
80cm
magnification x vs. y 70
80cm
53
Rapidity Gap Veto Acceptance Summary
Veto Acceptances
RPs
T2
T1
Veto
Acceptance
microstations at 19m?
h
Helsinki group Jerry Lamsa RO
TOTEM in combination with CMS represents an
experiment with a unique coverage in rapidity ?
collisions of extended sheets of QCD vacuum
branes in collision??
54
TOTEM Physics Scenarios
Proton b (m)
rapidity gap L(cm-2s-1)
jet
inelastic activity
g,e,m,t L, D,...
TOTEM CMS
TOTEM CMS
TOTEM CMS
elastic scattering
1540 18
beam halo?
1028 -1032
total cross section
inelastic acceptance
?1540
1028 -1033
soft diffraction
1540 170
gap survival
L, K, ,...
1029 -1031
mini-jets?
170 0.5
central fwd
jet acceptance
W, Z, J/?,...
hard diffraction
1031 -1033
central pair
di-jet backgr
b-tag, g, J/?,...
170 0.5
DPE Higgs, SUSY,...
1031 -1033
trigger
central fwd jets
di-leptons jet-g,...
mini-jets resolved?
170 0.5
low-x physics
1031 -1033
exotics (DCC,...)
p vs. po multiplicity
leptons gs,...?
jet anomalies?
0.5
1031 -1033