The CMSTOTEM Forward Physics Study

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The CMS/TOTEM Forward Physics Study

• Albert De Roeck (CERN)
• Physics with Forward Proton Taggers at the
  Tevatron and LHC

Introduction CMS/TOTEM Study Physics Detectors
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The Large Hadron Collider (LHC)

• PP collisions at
• ?s 14 TeV
• 5 experiments
• 25 ns bunch spacing
• ? 2835 bunches
• 1011 p/bunch
• Design Luminosity
• 1033cm-2s-1 -1034cm-2s-1
• 100 fb-1/year
• 23 inelastic events
• per bunch crossing

In LEP tunnel (circonf. 26.7 km)
TOTEM
Planned Startup April 2007
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The CMS experiment

• Tracking
• Silicon pixels
• Silicon strips
• Calorimeters
• PbW04 crystals
• for Electro-magn.
• Scintillator/steel
• for hadronic part
• 4T solenoid
• Instrumented iron
• for muon detection
• Coverage
• Tracking
• 0 lt ? lt 3
• Calorimetry
• 0 lt ? lt 5

A Huge enterprise !
Main program EWSB, Beyond SM physics
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The TOTEM Experiment
TOTEM physics program total pp, elastic
diffractive cross sections Apparatus Inelastic
Detectors Roman Pots (2 stations)
CMS IP
150 m
215 m
High ? (1540m) Lumi 1028-1030cm-2s-1 (few
days or weeks) gt90 of all diffractive
protons are seen in the Roman Pots. Proton
momentum measured with a resolution 10-3 Low
? (0.5m) Lumi 1033-1034cm-2s-1 215m
0.02 lt ? lt 0.2 300/400m 0.002 lt ? lt
0.2 (RPs in the cold region)
More on TOTEM acceptance by R. Orava/K.
Osterberg
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TOTEM inelastic detectors
T1/T2 inelastic event taggers ? T1
CSC/RPC tracker (99 LOI) ? T2 GEM or Silicon
tracker (TOTEM/New) ? CASTOR Calorimeter
(CMS/New)
TOTEM T2
T2
T2
T1
T1 3lt ? lt5 T2 5lt? lt6.7
CASTOR 9,71 ?I
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Forward Physics Program

• Soft Hard diffraction
• Total cross section and elastic scattering
• Gap survival dynamics, multi-gap events, proton
  light cone (pp?3jetsp)
• Diffractive structure Production of jets, W,
  J/?, b, t, hard photons
• Double Pomeron exchange events as a gluon factory
  (anomalous W,Z production?)
• Diffractive Higgs production, (diffractive Radion
  production?)
• SUSY other (low mass) exotics exclusive
  processes
• Low-x Dynamics
• Parton saturation, BFKL/CCFM dynamics, proton
  structure, multi-parton scattering
• New Forward Physics phenomena
• New phenomena such as DCCs, incoherent pion
  emission, Centauros
• Strong interest from cosmic rays community
• Forward energy and particle flows/minimum bias
  event structure
• Two-photon interactions and peripheral collisions
• Forward physics in pA and AA collisions
• Use QED processes to determine the luminosity to
  1 (pp?ppee, pp?pp??)

Many of these studies can be done best with L
1033 (or lower)
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Diffraction at LHC

• PP scattering at highest energy
• Soft Hard Diffraction
• ? lt 0.1 ? O(1) TeV Pomeron beams
• E.g. Structure of the Pomeron F(?,Q2)
  
• ? down to 10-3 Q2 104
  GeV2
• Diffraction dynamics?
• Exclusive final states ?
• Gap dynamics in pp presently not fully
• understood!

? proton momentum loss Reconstruct ? with
roman pots
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Example Di-Jet production
Reach in ? and ?

• Jet cross sections/events generation
• with POMWIG generator
• Cuts 0.001lt?lt0.1 and tlt1GeV2
• Pt gt 10, 100 GeV/c
• ?lt5 (CMS acceptance)
• Roman pot acceptance
• 200m 0.02lt?lt0.1
• 400m(?) 0.002lt?lt0.1
• (low lumi use rapidity gaps)

?
?
Bjorken-x of parton in the Pomeron
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DPE ? from Di-jet events

• Etgt 100 GeV/2 figs

Ptgt100 GeV/c for different structure functions
d? (pb)
events
H1 fit 6
(1-x)5
H1 fit 5
x(1-x)
H1 fit 6
H1 fit 4 (x 100)
?
?
??jets ET e-?/(?s ?) ? from Roman Pots ET
and ? from CMS
High ? region probed/ clear differences between
different SFs
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pp ? p jet jet p
Petrov et al.
ET gt 100 GeV
ET gt 10 GeV
t (GeV)
t dependence ? information on shape size of
the interaction region Evolution in the presence
of a short-time perturbation?
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Diffractive Higgs Production
Exclusive diffractive Higgs production pp? p H p
3-10 fb Inclusive diffractive
Higgs production pp ? pXHYp 50-200 fb
-jet
E.g. V. Khoze et al M. Boonekamp et al. B. Cox et
al.
gap
gap
H
h
p
p
Advantages Exclusive ? Jz0 suppression of gg?bb
background ? Mass measurement via missing mass
-jet
beam
dipole
dipole
p
New Under study by many groups
p
roman pots
roman pots
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MSSM Higgs
Kaidalov et al., hep-ph/0307064
100 fb
Cross section factor 10 larger in MSSM (high
tan?)
1fb
Also Study correlations between the
outgoing protons to analyse the spin-parity
structure of the produced boson
120 140
? See talk of A. Martin
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Beyond Standard Model
Diffractive production of new heavy states pp? p
M p Particularly if produced in gluon gluon
(or ??) fusion processes
Examples Light CP violating Higgs Boson MH lt 70
GeV B. Cox et al. Light MSSM Higgs h?bb at
large tan ? Light H,A (Mlt150 GeV) in MSSM with
large tan ? ( 30) ? S/B gt 10 Medium H,A
(M150-200 GeV) medium tan ?? V. Khoze et al.
(see AD Martin talk) Radion production -
couples strongly to gluons Ryutin,
Petrov Exclusive gluino-gluino production? Only
possible if gluino is light (lt 200-250 GeV)
V. Khoze et al.
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SM Higgs Studies
Needs Roman Pots at new positions 320 and/or
420 m Technical challenge cold region of the
machine, Trigger signals
Curves Helsinki Group Dots FAMOS simulation
Mass of Higgs
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Diffractive Higgs Production
Mass resolution vs. central mass from protons
measured in roman pots assuming DxF/xF 10-4

• Exclusive channel pp? p H p advantages
• Good mass resolution thanks to missing mass
• method
• DM O(1.0 - 2.0) GeV (including systematics)
• Study possible in the b-quark decay mode
• b-quark background suppression (JZ 0 states)!!
• Switch of dominant background (at LO)!
• Inclusive production pp? pXHYp
• 100 x larger cross section but background not
• suppressed (gain under study) and missing mass
• less effective

Mass resolution (GeV)
symmetric case
Central Mass (GeV)
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Detectors at 300m/400m

• Detectors in this region requires
  changes in the machine
• Physics Case
• Can we expect to see a good signal over
  background?
• ? Signal understood (cross section)
• ? Needs good understanding of the background
  (inclusive!)
• ? Needs more complete simulations
  (resolutions, etc.)
• Trigger
• 300m/400m signals of RPs arrive too late for the
  trigger
• ? Can we trigger with the central detector
  only for L1?
• Note L1 2-jet thresholds ET gt 150 GeV
• Machine
• Can detectors (RPs or microstations) be
  integrated with the machine? Technically there is
  place available at 330 and 420 m

Some Major Concerns
Of interest for both ATLAS and CMS
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Detectors at 300/400m

• Initial discussions with the machine group (early
  2002 see talk of D Marcina in the May CMS/TOTEM
  meeting)
• Cold section Detectors have to be integrated
  with cryostat
• No bypass option considered.

TOTEM presently not interested to follow this up
further with the machine. Common CMSATLAS
effort needed?
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Action is needed soon. Any change now means
paperwork!
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Low-x at the LHC

• LHC due to the high energy
• can reach small values of Bjorken-x
• in structure of the proton F(x,Q2)
• Processes
• ? Drell-Yan
• ? Prompt photon production
• ? Jet production
• ? W production
• If rapidities below 5 and
• masses below 10 GeV can be
• covered ? x down to 10-6-10-7
• Possible with T2 upgrade in TOTEM
• (calorimeter, tracker) 5lt?lt 6.7 !
• Proton structure at low-x !!
• Parton saturation effects?

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Low-x at the LHC
Rapidity ranges of jets or leptons vs x range
?lt5
5lt?lt7
Log10(x)
Log10(x)
7lt?lt9
5.5lt?lt7.8
Kimber Martin Ryskin
Log10(x)
Log10(x)
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Di-jets in pp scattering
Measurements for low-x (BFKL) dynamics
jet
??
jet
Azimuthal decorrelation between the 2 jets versus
rapidity distance between the 2 jets Large ??
range needed
Rise?
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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 poorly
know/constrained Models differ by factor 2 or
more Need forward particle/energy measurements
e.g. dE/d?
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Model Predictions proton-proton at the LHC
Predictions in the forward region within the
CMS/TOTEM acceptance
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Two-photon interactions at the LHC
Process
K. Piotrzkowski
WWA spectrum
Reach high W?? values!!
Relative luminosity S?? L??/Lpp 0.1 for Wgt
200 GeV Must tag protons at small t with good
resolution TOTEM Roman Pots!
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Two-photon interactions at the LHC
Sensitivity to Large Extra Dimensions
total ?? cross section W1000 GeV?
New studies ?p interactions with 10-100x ??
Luminosity
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SM HIGGS case
Number of Higgs events for single tags and
assuming integrated lumi-nosity of 30, 0.3 and
0.03 fb-1 for pp, pAr and ArAr collisions,
respectively.
SUSY
K. Piotrzkowski
Significant production rates and very clean
signatures available - both transverse and
longitudinal missing energy Exclusive
production! Range up to 200-250 GeV for single
tags
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?p interactions at the LHC
K Piotrzkowski

• 0.01 lt x lt 0.1, g tagging range
• 0.005 lt x lt 0.3, Bjorken-x range

g g luminosity spectra

• anomalous W and Z production at Wgq ? 1 TeV
• top pair production - top charge threshold
  scanning?
• single top production and anomalous Wtb vertex
• SM BEH - for example, g b ? H b, g q ? H W q
• SUSY studies (complementary to the nominal ones)
  -
• H t production (and H), b and t spairs, tc
  pair, ...
• Exotics compositness, excited quarks, ...

• p Physics
• Menu

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Luminosity
Example of a QED process for luminosity
monitoring
D. Bocian
pp ? pp ee-
Electrons are in forward range 5lt ? lt
8 Cross section ?barns Tracking important! EM
calorimetry essential Can get the luminosity to
1-2? So far gt 5 from W,Z production
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Status of the Project

• Common working group to study diffraction and
  forward physics at full LHC luminosity approved
  by CMS and TOTEM (spring 2002)
• (ADR/ K. Eggert organizing)
• Use synergy for e.g. simulation, physics
  studies forward detector option studies.
• Some of this happened e.g. RP T2
  simulation, detector options
• Detector options being explored
• Roman Pot/microstations for beampipe detectors
• at 150, 215 , add 310 420 m ? (cold
  section!)
• Inelastic detectors
• T1 CSC trackers of TOTEM (not usable at CMS
  lumi)
• Replace T2 with a compact silicon tracker (
  CMS technology) or GEMs
• Add EM/HAD calorimeter (CASTOR) behind T2
• Add Zero degree calorimeter (ZDC) at 140 m
• Common DAQ/Trigger for CMS TOTEM
• Common simulation etc

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New T2 Tracker Proposal (TOTEM)
Silicon tracker or GEM tracker
Distance from IP 13570 mm T2 inner radius 25
mm 8 mm 33mm  Vacuum chamber inner radius 25
mm Outer radius 135mm  Length 400 mm
CMS TRACKER Silicon Strip detectors Single
side p strips on n-type substrate, thickness320
mm, AC-coupled, pitch 80205 mm, Radiation
hardness up to 1.6x1014 1MeV equ./cm2, Cold
enviroment 20oC.
Or an 8 plan GEM detector?
T2 h range 5.3 lt h lt 6.5
Under study by TOTEM GEMs usable for CMS pp and
HI runs?
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A Forward Calorimeter

• A calorimeter in the range 5.3 lt?lt 6.8
  (CASTOR)

Position of T2 and Castor (7/2/03)
13570
T2
CASTOR
Tungsten and quartz fibres Length 152 cm
9?I Electromagnetic section 8 sectors/ needs
extension
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CASTOR PROTO BEAM TEST
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Installation of T2 tracker/CASTOR
CASTOR shielding
T2
HF
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ZDC zero degree calorimeter
ZDC
ZDC
Beam pipe splits 140m from IR
ZDC LOCATION
M. Murray
Tungsten/ quartz fibre or PPAC calorimeter EM
and HAD section Funding pending in DOE
BEAMS
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Opportunities for present/new Collaborators

• CMS central detector
• Diffractive Gap Trigger (possible in CMS trigger
  but needs to be studied)
• T2 region
• Calorimeter (CASTOR)
• Add ? granularity (silicon, PPAC,)
• Castor trigger
• So far only one side of CMS equipped (500 kCHF)
• T2 tracker (part of TOTEM, but still in flux)
• May need participation from CMS (if silicon
  option)
• May need new tracker by CMS (if GEM option)
  watch TOTEM TDR
• Detectors at 300/400m
• Completely new project
• Needs new resources (there are interested parties
  in CMS ATLAS)
• ZDC small project but funding not yet
  garanteed
• New detectors in the range 7lt? lt9??? (20 m from
  IP)
• ? Certainly help welcome on simulation
  tools, detailed physics studies

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Rapidity Gaps at LHC

• Number of overlap events versus LHC luminosity
• distribution
  of number of interactions

1.1033
2.1033
1034
1033
1032
1 int. 22 4
Doable at startup lumnosity without Roman Pots!
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Gap moves farther from outgoing proton for
smaller xPOM
xPomeron lt 0.03 xPomeron lt 0.02 xPomeron lt
0.0075
POMWIG Hard Single diffraction
? of minimum-? particle per event
? G. Snow
rapidity gap trigger study
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Groups that expressed interest (my interpretation)

• Athens Proposes to built one CASTOR
• Annecy Physics and Roman Pot studies/
  Hardware participation in T2
• Belgium Interest in Roman Pots Hardware
  (detectors RD39)
• Detector layout/radiation
  hardness/occupancy/trigger/integration
• Gamma-gamma /gamma-p
  studies/Low-x studies/Fast simulation.
• CERN Radiation studies
• Physics studies on
  diffraction and low-x
• Nebraska Trigger with gaps including CASTOR,
  Luminosity
• Texas Univ ZDC Hardware
• UCLA DAQ (CMS/TOTEM connection), Physics
  studies in future
• North-Eastern APDs for CASTOR readout
• Helsinki Micro stations hardware RD and
  Beamline simulation studies
• Brazil Diffractive studies RPs in cold
  section
• Saclay Roman pots in cold section?
• Protvino Background calculations for RPs
• ITEP Participation in CASTOR via INTAS
  project
• Moskou Physics Studies/ CASTOR hardware
• Karlsruhe Cosmic ray interest.
• Buenos Areas QCD/diffractive studies/ Hardware
  interest to be defined

Preliminary
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Summary

• A study group has been formed to explore the
  common use of CMS and TOTEM detectors and study
  the forward region.
• Physics Interest
• - Hard ( soft) diffraction, QCD and
  EWSB (Higgs), New Physics
• - Low-x dynamics and proton structure
• - Two-photon physics QCD and New
  Physics
• - Special exotics (centauros, DCCs
  in the forward region)
• - Cosmic Rays, Luminosity measurement,
  (pA, AA)
• Probably initial run at high ? (few days/weeks
  ? 0.1-1 pb-1 )
• Runs at low ? (10-100 fb-1 )
• NEW CMS officially supports forward physics as a
  project!
• Expression of interest for the LHCC
• Opportunities for present/new collaborators to
  join
• ? complete forward detectors for initial
  LHC lumi