Forward Physics Measurements

1
Forward Physics Measurements
at the LHC
Risto Orava University of
Helsinki and Helsinki
Institute of Physics
Diffraction 2006
Milos 5. 10. September
2006
2
Leading Protons measured at -420m, -220m -147m
from the CMS
Forward Physics at the LHC
Castor
Leading Protons measured at 147m, 220m and
420m from the CMS
T2
CMS
T1
T1
T2
Castor
Leading protons RPs at ?147m, ?220m and
420m Rap gaps Fwd particle flows T1 T2
spectrometers Fwd energy flows Castor ZDC
Veto counters at ?60m ?140m?
CMS Totem fp420 -unique fwd experiment
Diffraction 2006 Risto Orava
Milos 5. 10. September 2006
3
gtgt LP 420m
4
LHC Experiments pT-h coverage
CMS fwd calorimetry up to h ? 5 Castor ZDC
1000
CMS
ATLAS
100
T1
T1
pT (GeV)
ALICE
LHCb
10
T2
T2
1
microstation
microstation
CASTOR
CASTOR
RP
RP
0.1
veto
veto
pTmax ?s exp(-h)
ZDC
ZDC
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.
fp420m
R. Orava Diffraction 2006 Milos Island
5
LHC measurements - basis
CMS Tracking Calorimety

• Total pp cross section with a
• precision of ? 1
• Elastic pp scattering
• 10-3 ? t (p?)2 ? 10 GeV2
• Leading particles
• 2?10-3 ? ? ? 2 ? 10-1
• Particle flows, rap gaps
• 3.1 ? ? ? 4.7 and 5.3 ? ? ? 6.5
• Investigate diffractive forward phenomena
  together with CMS
• ( CMSCastorZDCfp420m)

TOTEM Castor, ZDC, 420m
TOTEM Castor, ZDC, 420m
simulation by V. Nomokonov/Helsinki group
HERA and Tevatron studies as guidance!
Note Rapidity coverage could be further improved
by veto counters at ?60m to ?140m, microstations
at 19m etc.
6
b1540m, 90m, 18m, 2m, 0.55m,...protons
Jerry Lämsä RO/Helsinki group
b1540m optimized for small t b90m
optimum for soft semihard
diffraction b2m,18m useful for hig-t
elastics b0.55m required for hard
diffraction, Higgs,...
7
Different LHC Run Options Complementary
Physics Scenarios at the LHC

• The nominal LHC optics (b 0.55m)
• high luminosities and large -t acceptance for
  studies of hard diffraction, small-x physics and
  new particle searches in SM and MSSM scenarios
• (2) The nominal TOTEM optics (b ? 1540 m,
  parallel-to-point focusing in both planes)
• low luminosities and very small -t acceptances
  for precision studies of elastic scattering and
  soft diffraction
• (3) The custom optics at b 90 m
  (parallel-to-point focusing in vertical plane)
• medium luminosities, very small ? and small -t
  acceptances for early studies of elastic
  scattering, soft and semi-hard diffraction
  studies
• (4) The custom optics at low b (b 2 m etc.
  during the run-in phase of the LHC)
• high luminosities and large -t acceptance1 for
  first studies of semi-hard and hard diffraction,
  and low-x physics.

1 Also small -t values can be reached with
reduced acceptance.
8
LHC Run Scenarios
9
Elastic cross section Significance
dsel/dt yields

• pp interaction radius (slope in dsel/dt)
• total pp cross section (with the inelastic rate)
  
• Coulomb-nuclear Interference (expected to have an
  effect over large interval in t).
• ratio of the real and imaginary parts (through
  dispersion relations, a precise measurement of r
  will constrain stot at substantially higher
  energies)

Complementary run scenarios at the LHC
V. Kundrat et al.
10
Elastic cross section Measurements

• Leading proton detectors at ?147, ?220 and
  420m meters from the Interaction Point
  (IP5)1.
• The nominal TOTEM beam optics set-up has high b
  (b ? 1540 m), and no crossing angle
• at the IP for optimizing the acceptance and
  accuracy at small values of t down to -tmin ? 2 ?
  10-3 GeV2.
• The -t distribution is extrapolated to -t 0 ?
  the total proton-proton cross section by the
  Optical
• theorem to better than 1.
• The custom optics of b 90 m allows a first
  quick measurement of the elastic cross section
  dsel/dt
• ? extrapolation to the Optical point with an
  accuracy of a few percent.
• Short runs with other LHC custom optics set-ups,
  such as the injection optics (b 18 m), or
  stage-1
• 'pilot' run optics (b 2 m) allow
  measurements up to -t ? 10 ? 15 GeV2.
• Runs with a reduced center-of-mass energy (Ebeam
  450 GeV) will allow an analysis of energy
• dependence, comparisons with the Tevatron
  results and a precise measurement of the r
  parameter.

1 The detector locations at ?145 and ?149
meters from IP5 are here referred as the ?147
meter location and the ones at ? 218 and ? 222
meters from IP5 as the ?220 meter location. 2
The closest approach to the beam is of the order
of a few mms (10s 0.5 mm) and depends on the
measurement location and used beam optics scheme
(see ?1.2?).
11
TOTAL DIFFRACTIVE CROSS SECTIONS stot and
sSD
total pp cross section
single diffractive cross section
TOTEM
TOTEM
random choice of models
stot ?mb?
sSD ?mb?
LHC
LHC
?s ?GeV?
?s ?GeV?
figs. from Sapeta

• measurement of stot to 1 will distinguish
• between different models

• measurement of sSD to 10 allows tests
• of diffractive models

• stot ? (lns)e as s ? ?
• 0, 1, 2, or - 0.08 ??

R. Orava Diffraction 2006 Milos Island
12
Total cross section Significance

• pp cross section measurements at Tevatron
  energies are
• ambiguous and the energy dependece of stot
  poorly constrained
• ? Even a total cross section which decreases
  with energy, cannot
• be ruled out)
• ? A precise measurement of stot at the LHC will
  discriminate
• between fundamentally different theoretical
  scenarios.
• With a simultaneous measurements of the elastic
  and inelastic
• rates, the luminosity can be accurately defined
  
• ? precision physics studies.

13
The minimum-bias events should be
understood, too...
The minimum-bias energy flows populate the
forward detectors ... while the central
detectors are floded by a large multiplicity of
soft particles...
simulated distributions by Jerry Lamsa/Helsinki
group
Underlying events probed by the forward tags.
14
Single diffraction Significance

• Single diffractive dissociation to a large mass
  system, M, is not fully
• understood
• Both the triple-Pomeron based description and
  prediction of "multi-Reggeon"
• events - events with a few large rapidity gaps
  - lead to sSD that grows faster
• than stot.
• A measurement of sSD and the cross section of
  multiple large rapidity gaps at
• the LHC will test the proposed models (see
  CDF/Dino, Uri Maor, KMR).
• For understanding the asymptotics of the strong
  interaction amplitude, it is
• crucial to measure the -t-dependence of sSD.
• Vanishing of triple-Pomeron coupling, G3P, at
  -t ? 0, might cure the problem of
• excessive sSD
• A measurement of the cross section dsSD/dt at t
  ? 0, would test the 'weak
• coupling' scenario

15
Single diffractive energy flows populate the
forward detectors ...while much of the
soft particle multiplicities are seen in the
central system.
simulated distributions by Jerry Lamsa/Helsinki
group
16
Single diffraction Significance...

• Measurement of the location of the diffractive
  minimum (predicted as
• a result of the destructive interference
  between the pole and cut
• contributions)
• ? further testing of the 'weak coupling' scheme.
• Screening corrections' due to multi-loop
  Pomeron graphs
• gap survival factor S2 ? 0 when s ? ?, or gap
  size Dh ? ??
• investigate the dependence of S2 on c.m.s.
  energy, gap size and the
• number of gaps.-gt see Uri Maor
• SD dominated by the periphery of the interaction
  disk?
• particles produced within the diffractive system
  have smaller average
• transverse momenta (compared to the
  secondaries at energies ?s ? M)?

17
Single diffraction Measurements

• Based on tagging leading protons and rapidity
  gaps in inelastic events.
• The cross sections are typically large, short
  special runs with the nominal TOTEM
• high b optics conditions (b ? 1540 m) yield
  excellent statistics.
• The pilot runs with b 90 m, 18 m - 2 m,
  planned for the initial stages of the
• LHC operation, suit well for measurements of
  soft diffractive scattering.
• About 85 (50) of the diffractive protons with
  the nominal b 1540 m (special
• b 90 m) are registered and with a
  diffractive mass, M, acceptance better than
• 50 down to M 3 GeV (1.2 GeV?).
• The diffractive systems are measured over the
  full azimuthal angle and the
• diffractive protons within the acceptance of
  the elastic ones.
• At low diffractive masses, the acceptance could
  be importantly - extended down
• to ?1.2 GeV (?) by installing additional veto
  counters at 60 to 140m.

18
Semi-hard diffraction Significance
CDF D0 results for SD/incl. ratio

• Soft diffractive dynamics objects signifying
  the hard scale high ET jets, heavy quarks,
• heavy bosons, new heavy particles?
• ? measurement up to rapidities of ?h ?? 6 probes
  quark and gluon structure of diffraction1

a compilation by H. Abramowicz

• The ratio b ? xBj/? interpreted as the momentum
  fraction of a parton within the
• Pomeron.

1 However, it is known that in low impact
parameter reactions, a single Pomeron does not
dominate diffraction...
19
Single diffraction Strategy

• The kinematics of these events is defined by the
  invariant mass and
• pseudorapidity of the diffractive system.
• The measurement aims at reconstructing the
  produced hard objects
• within the full acceptance region of the
  TOTEM?CMS set-up.
• Semi-hard diffractive events are recorded during
  the custom and nominal
• runs with b? ? 1540 m, 90 m, 18 m and 0.55m for
  diffractive masses of
• M? gt 3 (1.1) GeV
• SD production of B-mesons decaying into J/?
  studied by the Rio group

20
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21
Low-x physics Significance

• The detection of low-x processes is based on
  tagging the objects (jets, heavy quarks, heavy
  bosons) that signify a hard scale in both central
  and forward rapidities.
• TOTEM?CMS could test a number of specific
  predictions based on the optical low-x model by
  Frankfurt, Strikman and Weiss by measuring
• The type of leading particles nucleons and N
  states.
• Transverse momenta of the leading particles for
  p? ? 1 GeV/c.
• Correlations between the transverse momenta of
  leading hadrons.
• Particle flows for particles in the fractional
  momentum region of z ? 0.02 -
• 0.05 in both fragmentation regions (long range
  rapidity correlations) and
• particle/energy flows of h 4 - 6.

22
Low-x measurements Strategy

• The aim of the TOTEM?CMS set-up is to measure
  jets at rapidities h ? 6 up to transverse
  energies of ET ? 10 GeV to reach x ? 10-6 ?
  transform LHC into a deeply inelastic scattering
  (DIS) machine.
• Correlations between the forward (x ?? 10-2) and
  central jets (x ? 10-2), heavy
• quarks and heavy bosons ? proton - parton
  configurations in three dimensions.
• Forward jets in triggering for new phenomena in
  high-ET central processes.
• The CASTOR calorimeter covers the pseudorapidity
  region of 5.4 ? h ? 6.7,
• similar to the coverage of the T2 tracking
  station ? measure the forward jets.
• With a modest (veto)detector upgrade, the
  rapidity acceptance could be
• extended up to ?h?? 11 ? reach x ? 10-8 .

23
xBj vs. Q2 acceptances
x-Q2 acceptance plots by Erik Brucken/Helsinki
group
24
Drell Yan process with CASTOR
P. van Mechelen, S. Ochesanu (Antwerp), E.
Sarkisyan-Grinbaum (Manchester)
M2lls x x-
Gives access to low-xBJ partons in proton in case
of large imbalance of fractional momenta x1,2 of
leptons, which are then boosted to large
rapidities CMS CASTOR calorimeter range 5.3
? 6.6 gives access to xBJ10-7 CASTOR has 16
segments in azimuth and logitudinally has
electromagnetic and hadronic section CASTOR
alone can provide crude estimate of Mll Can be
much improved with information from Totem tracker
T2 in front of CASTOR
25
Triggering on Drell Yan with CASTOR
P. van Mechelen, S. Ochesanu (Antwerp), E.
Sarkisyan-Grinbaum (Manchester)

• DrellYan signal
• High electromagnetic energy
• Small hadronic energy fraction
• One charged track
• QCD background
• Rapid decrease of number of segments with large
  electromagnetic energy
• Symmetric electromagnetic and hadronic energy
  depositions
• Low charged multiplicity
• ? separation between signal and background
  possible at L1 ?
• Under study

26
Central diffraction Significance

• A good environment for the production of
• exotic meson states (glueballs, hybrids,...)
  
• via gg ? M in
• pp ? p M p
• - 90 m optics could be used for this!
• A strong coupling for glueballs and hybrids
• as a result of the assumed two-gluon
• exchange?
• High statistics studies possible with the
• 'gluon collider' mode of the LHC.
• Here azimuthal correlations with the quasi-
• elastic pair of leading protons can be
• particularly significant.

27
Central diffraction Significance...

• Heavy quark systems could be produced
  exclusively in CED (see KMR)
• - First indications have been reported by the
  CDF Collaboration at the Tevatron
• ? ?b0(1P) (m 9859.9 ? 1.0 MeV), with an upper
  limit of Br(g?(1S)) 6.
• - The decay upsilon subsequently decays into ? ?
  l l - with 2.5 branching ratio into each
  lepton species
• The signature is remarkable nothing but l l
  g in the entire central detector.
• - The low E? of the photon complicates the
  trigger, however

28
Central Diffraction

• The Hard Central Exclusive
  Diffractive (CED) processes
• pp ? p MX
  p,
• will extend the
  physics programme at the LHC.
• The process facilitates both QCD asymptotics and
  searches for physics beyond the
• standard model.
• Rapidity gaps (when available) provide a clean
  environment for investigating the
• signal events experimentally.
• A colour singlet state, MX, is produced with a
  minimal background from soft
• secondary particles LHC is turned into a
  gluon factory.

For low mass CD interactions, short runs with the
custom optics (b 90 m and 1540 m). For the
CED Higgs events (central masses below 250 GeV),
the leading proton measurement stations at 420 m
and the nominal LHC optics with b ? 0.55 m is
required. For central masses in excess of 250
GeV, low-b conditions together with the leading
proton measurement at the 220 m location are
needed.
29
MX acceptances vs. run scenario ? 220 m
- symmetric pairs of leading protons
b 2 m
b 0.55 m
acceptance
acceptance
MX(min) ? 250 GeV
MX(min) ? 250 GeV
acceptance figures based on analyses by Mikael
Ottela Kenneth Österberg/Helsinki group
MX ?GeV?
MX ?GeV?
MX(min) ? 3 GeV
b 90 m
b ? 1540 m
acceptance
acceptance figures based on analyses by Mario
Deile Valentina Avati
acceptance
MX(min) ? 3 GeV
MX ?GeV?
MX ?GeV?
30
- t acceptances vs. run scenario ? 220 m
-tmax ? 10 GeV2
-tmax ? 10 GeV2
- t ? 0.8 GeV2
acceptance
acceptance
b 0.55 m
b 2 m
-t0.25 GeV2 ? 31
-t0.25 GeV2 ? 31
acceptance figures based on analyses by Mikael
Ottela Kenneth Österberg/Helsinki group
- t ?GeV2?
- t ?GeV2?
- t ? 0.001 GeV2

• t ? 0.01 GeV2
• depending on ?

b ? 1540 m
b 90 m
acceptance
acceptance
acceptance figures based on analyses by Mario
Deile Valentina Avati
-tmax ? 0.6 GeV2
-tmax ? 1.2 GeV2
-t ? 10-2 GeV2 (depending on ?)
-t ? 10-3 GeV2 (depending on ?)
- t ?GeV2?
- t ?GeV2?
31
Central Diffraction Mass resolution for
220m?-220m
Increasing symmetry of the proton pairs
acceptance figures based on analyses by Mikael
Ottela Kenneth Österberg/Helsinki group
32
A historical note....
5.13
CED Mass Measurement at 420m...
Mass resolution vs. central mass assuming DxF/xF
10-4
DM (1.5 - 3.0) GeV (DxF/xF (1-2)?10-4)
Mass resolution (GeV)
stable result since 2001
symmetric case
? 65 of the data
Helsinki group/J.Lamsa, R.O.
20 GeV lt MX lt 160 GeV (MXmax determined by the
aperture of the last dipole,B11, MXmin by the
minimum deflection 5mm)
Central Mass (GeV)
Workshop on Diffractive Physics 4. 8. February
2002 Rio de Janeiro, Brazil
33
leading protons at ? 420 m - b 0.55 m
? acceptances
? resolutions
beam-1
all uncertainties
resolution ?(?)/?
acceptance
acceptance figures based on analyses by the
Helsinki group
beam
vx
beam-2
detector
beam pos.
?
?
beam energy spread 1.1 ? 10-4
vx transverse vx position 10 mm
detector resolution 10 mm
beam position resolution 50 mm
34
Central Exclusive Process pp ? p X p
MX acceptances
ExHuME 1.0
PHOJET 1.12
220m 420m
220m 420m
acceptance
acceptance
acceptance figures based on analyses by the
Helsinki group
420m 420m
420m 420m
MX GeV
MX GeV
35
Central Exclusive Process pp ? p X p
MX resolutions
220m 420m (ExHuME 1.0 PHOJET 1.12)
acceptance figures based on analyses by the
Helsinki group
s(MX)/MX
420m 420m (ExHuME 1.0 PHOJET 1.12)
MX GeV
36
CED of a light SM/MSSM Higgs

• Selection rules result in the central system
  being (to good approx) JPC 0, thereby
  reducing the dominant gg ? b bbar background to H
  ? bbar decay
• For SM Higgs Fighting chance with S/B1, though
  low event yield
• But proton tagging may be the discovery channel
  in the MSSM

Studies by Marek Taevský (Physics Inst. Prague
Univ.Antwerp) H-gtWW in SM
hep-ph/0505240 H-gtWW(bb,tautau) in MSSM
Ongoing H-gtbb
Tuning of cuts Comparison of models
Proceed. HERA-LHC Models vs. Data
Ongoing Background from
coincidence of non-diff events with diff pile-up
under study Trigger major limiting factor, see
further..
37
Inclusive CD and SD ttbar production
Detect ttbar in semileptonic decay channel pp ?
pX(tt)Xp tt ? bbqq???
Event yield after cuts CD case between 1 and
10 per 10 fb-1, depending on theoretical
model(Sudakov!)Backgrounds under
studydiffractive other ttbar decay channels, W
jetsnon-diffractive inclusive ttbar in
coincidence with protons from diff pile-up
eventsCMS muon trigger thresholds not a
limiting factor in event yield
38
Photon physics with roman pots
Krzysztof Piotrzkowski Université Catholique de
Louvain
Louvain group J. de Favereau, V. Lemaître, Y.
Liu, S. Ovyn, T. Pierzchala, K. Piotrzkowski,
X.Rouby

• Investigate potential of studying in CMS
  high-energy photon interactions
• Three main areas
• SM tests in gg interactions
• SM tests in gp (gA) interactions
• Luminosity with lepton pairs ( diffractive
  meson photoproduction)

• Areas of activity
• Calibration candle Muon pairs two-photon
  production (Y.Liu)
• WW (and ZZ) case (J. de Favereau T.
  Pierzchala)
• Single W photoproduction (J. de Favereau)
• WH photoproduction (M. vander Donckt et al.)

39
Photon physics with roman pots II
Exclusive lepton pairs
known
Key signature Acoplanarity angle for dileptons
Calibration process both for luminosity and
energy scales, has striking signatures and can
be well triggered and reconstructed by CMS
gg ?ll
DY?qq ?ll
DY?qq ?ll
40
Acceptance in ? -t vs. Run Scenario
Acceptance of leading protons produced in Central
Diffractive events (Phojet)
30 acc. contours
log?
Acceptance
b 2m
FP420m
acceptance figures based on analyses by the
Helsinki group and Valentina Avati Mario Deile
b 90m
b 1540m
b 90m
b 1540m
b 2m
log(-t)
log(-t)
b 90m CD protons detected by their
scattering angle in the vertical RP detectors,
-t ? 3? 10-2 GeV2, almost
independently of ?, ? 50 of CD protons seen
(standard LHC injection optics, p-to-p in
vertical plane ?


horizontal displacement proportional to ? vx
positon/CMS) b 1540m -t ? 1? 10-3 GeV2, ? 85
of CD protons seen (very low t reach) b 2m
CD protons seen in the horizontal detectors,
only, 0.02 ? ? ? 0.1, -t ? 2 GeV2, poor
acceptance (high t) (420m
RPs with ?min ? 0.002 would help!)
41
Background in leading proton measurement

• Beam halo beam protons diffusing out from the
  closed orbit
• Beam-gas inelastics (fixed tgt exp!) from
  beam-gas interactions (simulated from upstream
  TAS to lp locations) rate lt a few 100 Hz
• pp inelastics forward particle flow from IP5 the
  main worry

Single arm background rates from p-p coll.
(preliminary)
Background analysis by Mario Deile/CERN
42
A new tool for leading proton simulation

• A Geant3 simulation package for the
• leading particles has been worked out by
• Jerry Lämsä.
• The package hass being validated and
• includes all the beam elements that are
• relevant for tracing the leading particles
• originating at the IP (5 or 1) up to the
• 420 lp detector location.
• Being used for acceptance, resolution
• and background studies.

Note The illustration above only describes the
outgoing lps.
43
Movable beam pipe at 420 meters
hit score plane
hit score plane
hit score plane
beam axis

• detector distance vs. beam 3 mm
• length of the movable section 7 m
• movement 16 mm
• wall thickness 0.3 mm

Si detectors
Si detectors
70 mm
Si detectors
?426 m
Jerry Lämsä RO/Helsinki group
44
a proton interacts in the beam pipe
Jerry Lämsä RO/Helsinki group
45
IP originated background hits in ?420 m detectors

• 1st results based on 0,5 million Single
  Diffractive Events (PHOJET 1.12)
• where a leading proton collides with the beam
  pipe

Wall thickness in the movable beam
pipe Background rate 300 mm 2 ?
10-5 600 mm 3.4 ? 10-4 - single hit
in each of two detectors separated by 7 meters at
the ?420 m location
simulation results by Jerry Lämsä/Helsinki group
46
Diffractive trigger stream in CMSThe difficulty
of triggering on a light Higgs
The CMS trigger
A.1, B.1

• 120GeV Higgs has L1 jet trigger signature 2
  jets (ET lt 60 GeV) in CMS Cal
• Measured L1 jet ET on average only 60 of true
  jet ET
• L1 trigger applies jet ET calibration and cuts on
  calibrated value
• Thus 40 GeV (calibrated) 20 to 25 GeV measured
• Cannot go much lower because of noise
• Use rate/efficiency _at_ L1 jet ET cutoff of 40 GeV
  as benchmark
• L1 2-jet rate for central jets (hlt2.5) _at_ L1 jet
  ET cutoff of 40 GeV for
• Lumi 2 x 1033 cm-2 s-1 50 kHz , while
  considered acceptable O(1 kHz))
• Need additional conditions in trigger Forward
  detectors !

trigger analyses by Monika Grothe et al.
47
L1 output rate reduction with fwd detectors

• Very good reduction of rate in absence of
  pile-up both with T1/T2 veto
• and with near-beam detectors at 220/420m
• However, reduction decreases substantially in
  the presence of pile-up because
• of diffractive component in pile-up

Richard Croft, Bristol
Achievable total reduction 10 x 2 (HT cond) x 2
(topological cond) 40
Can win additional factor 2 in reduction when
requiring that the 2 jets are in the same ?
hemisphere as the RP detectors that see the
proton
Jet isolation criterion
For dijet trigger adding L1 conditions on the
near-beam detectors provides a rate reduction
sufficient to lower the dijet threshold to 40GeV
per jet while still meeting the CMS L1 bandwidth
limits for luminosities up to 2x 1033 cm-1 s-1
trigger analyses by Monika Grothe et al.
48
Extending acceptance in M by veto counters
Jerry Lämsä RO/Helsinki group
49
50 for M 3.4 (1.4) GeV
high-b
50 for h 8.8 high-b
50 for h 9.4 low-b
50 for M 3.4 (1.4) GeV
low-b
simulations by J. Lämsä/Helsinki group
50
TOTEM?CMS Physics Reach
TIME?
51
Physics priorities vs. the initial phases of the
LHC Elastic scattering stot

• b 2m-18m??
• dsel/dt (large t)
• (2) b 90m
• dsel/dt (moderate t)
• stot L(quick dirty?)
• (3) b 0.55m
• dsel/dt (large t)
• (4) b 1540m
• dsel/dt (small t)
• stot L (TOTEM TDR)

TIME?
52
Physics priorities vs. the initial phases of the
LHC Single diffraction low-x

• b 2m -18m??
• dsSD/dxdt (limited acc.)
• (2) b 90m
• dsSD/dxdt (50 acc.)
• semi-hard diffraction
• low-x phenomena
• (3) b 0.55m
• dsSD/dxdt (limited acc.)
• low-x phenomena
• (4) b 1540m
• dsSD/dxdt (85 acc.)

CMS Tracking Calorimety
TOTEM Castor, ZDC, 420m
TOTEM Castor, ZDC, 420m
TIME?
53
Physics priorities vs. the initial phases of the
LHC Central diffraction

• b 2m, 6m, 18m??
• dsCD/dMXdt (hard CD?)
• (2) b 90m
• dsCD/dMXdt (soft semihard CD)
• (3) b 0.55m
• dsCD/dMXdt (hard CD, discoveries)
• (4) b 1540m
• dsCD/dt (soft CD, x-t coverage!)

TIME?