Exclusive Higgs Production at LHC Summary for Discussion

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Exclusive Higgs Production at LHC Summary for
Discussion

• Albert De Roeck (CERN)

The Physics The Issues Work Needed
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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
?M O(1.0 - 2.0) GeV
p
Under study by many groups
p
roman pots
roman pots
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Light Higgs
Khoze, Martin,Ryskin Orava, ADR
hep-ph/0207042 Different processes for light
Higgs discovery at the LHC
Revision resolution 2?
Numbers for 30 fb-1 and a Higgs of 120 GeV A
light Higgs will be a challenge for the
LHC!
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Higgs Studies
SM Higgs (30fb-1) 11 signal events (after cuts
O(10) background events Cross section factor
10-20 larger in MSSM (high tan?)
100 fb
Kaidalov et al., hep-ph/0307064
1fb
?Study correlations between the
outgoing protons to analyse the spin-parity
structure of the produced boson
A way to get information on the spin of the
Higgs ?ADDED VALUE TO LHC
120 140
Also suppose h?W,Z coupling small..
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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.
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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Note in passing

• Incoming particles are gluon
• ? Gluon factory!

• 100,000 high purity (q/g 1/3000) gluon jets
• with ET gt 50 GeV in 1 year
• Possible new resonant states, glueballs,
• quarkonia 0 (?b ),gluinoballs, background
• free environment (bb, WW tt- decays)
• Squark gluino threshold scans?
• - thresholds are well separated
• - practically background free signature
• multijets missing transverse energy
• - model independence (missing mass!)
• - expect 10-15 events for gluino/squark masses
• of 250 GeV
• - (interesting scenario gluino as the LSP with
• mass window 25-35 GeV (S.Raby et al.) )

M
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Two-photon interactions at the LHC
Process
K. Piotrzkowski
WWA spectrum
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
SUSY
Relative luminosity S?? L??/Lpp 0.1 for Wgt
200 GeV Must tag protons at small t with good
resolution Roman Pots!
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We know that there are issues

• Small cross sections (for the SM Higgs)
• Limited efficiency (acceptance, B-tagging)
• Backgrounds (inclusive) full simulations needed
• Need upgrade of the detectors or machine
• 300/400m
• What detectors (1.9K? Cold? Warm?), mechanics,
  access,?
• Level -1 Trigger how to keep the events w/o RP
  info
• Mass resolutions, allignement etc.
• Machine
• Detectors in the cryostat?
• Can we have an optics to accept the pHp events lt
  220m?

Will need study groups to tackle these questions
(experimentsmachine
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Physics

• SM Higgs cross sections low few 10 of events
  after acceptance cuts
• Can we get more confidence in the
  calculations?
• ? check with Tevatron and LHC
  data
• Measure exclusive DPE processes with a hard scale
• Dijets
• 2 photon events
• Exclusive ? states
• Measure the ET dependence of such processes
• What are the uncertainties on the calculations?
• Eg Khoze et al factor 2-3
• Lower limit QED cross sections 0.1 fb-1

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Test for Exclusive Production
There is a published measurement of double
diffractive dijet production from Run I from CDF,
CDF data
CDF di-jets in DPE Upper limit 3.7 nb Generally
predictions of gtO(100) fb for the
Higgs overshoot this predictions by a factor
10-100 Hence ? ruled out! CDF and D0 should
find measure a signal inrun II
Smooth decrease of the cross section. Can
exclusive processes be seen on top of the
non-exclusive background?
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Test for exclusive production
D. Goulianos
New (June 2003) RUN-II DPE data with larger
statistics
V. Khoze et al prediction for exclusive DPE 1
nb
More tests with upcoming Tevatron run-II data
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Detecting pp?pHp
TOTEM apparatus Inelastic Detectors Roman
Pots
CMS IP
150 m
220 m
High ? (1540m) Lumi 1028-1031cm-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
? NOT FOR THE EXCLUSIVE Higgs (maybe DPE
jets or ??) Low ? (0.5m) Lumi
1033-1034cm-2s-1 220m 0.02 lt ?
lt 0.2 ? No acceptance for exclusive Higgs
300/400m 0.002 lt ? lt 0.2 ? Acceptance for
exclusive Higgs
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Measuring pHp with existing RPs?

• Changing the optics to increase the acceptance
  for
• lt 220 m RPs, e.g. by adding/changing
  magnets (D1).
• first (modest) attempts show that it is not
  straight forward (W. Herr, R. Orava, J. Lamsa)
• Increase the acceptance for the roman pots
• Go closer to beam not very likely (what could
  one stretch? Now assumed 10? 0.5mm)
• However these options should be pursued to the
  end, since it would make life a lot easier
  (trigger/cryogenics etc.)
• High Luminosity cannot be compromised for
  CMS/ATLAS
• Needs a task force, i.e. interested person(s)
  working together with CERN machine experts.

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DPE Exclusive Higgs Production
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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Front-end/Trigger Timing Model (CMS)
ATLAS 2.5 ?sec
Practical maximum distance
220-230 m
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Trigger

• Signals from 300/400 m will not be in time for L1
  trigger of CMS (ATLAS)
• Could be available for L2/ but needs work
• Maximum total rate at L1 50/100 kHz
• L1 ET threshold for 2 jets is 170 GeV at low
  luminosity
• Need to design a special topological triggers
• Pile up at gt 1033 cm-2s-1 destroys rapidity gaps
• Cannot us B-tagging at CMS in L1, but large
  flexibility with calorimeter quantities (jet
  ETs, ?, ?, exclusiveness)

? several studies ongoing but no white smoke yet.
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Higgs Jet Characteristics
C. Royon/Detector study for CMS
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Trigger Studies
R. Orava et al
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Resolutions
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Resolutions
Helsinki group
Can we improve the resolution? ? would increase
significance
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Detailed simulation studies
Detailed studies are starting now Boonekamp/ATLAS
Royon/CMS Include exclusive and inclusive bb
background Include missing mass resolution (not
correctly used correlations!!- resolution should
be 1.5-2 better than shown here)
100 fb-1
First look/still being optimized
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Detectors at 300/400m

• Initial discussions with the machine group (early
  2002 D. Marcina)
• Cold section Detectors have to be integrated
  with cryostat
• Is a bypass an option? 15m cold-warm
  transition SC services

? Many machine components already ordered,
some already delivered ? Machine wants easy
start-up/no perturbation ? Change means an
LHC upgrade (phase II)
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Detecting an off-momentum proton
At 420 m an off-momentum proton lies between the
two beam pipes which are at 1.9 K! D 2
m?p/p 0.5 ?x 10 mm i.e. still inside
the beampipe But 10 beams 3mm
K. Potter
Detectors to measure the protons? Mechanics,
access etc.? Allignment, calibration issues
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Roman Pot Detectors with Silicon e.g.
Example C. Da Via
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Alternative Detectors
?-station concept (Helsinki
proposal) Silicon pixel or strip detectors in
vacuum (shielded), 3D silicon
Very compact Maybe for detectors at 400 m? Needs
test-setup
Movable detector
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Diffraction at the LHC

• Common working group to study diffraction and
  forward physics at full LHC luminosity (ADR/
  K. Eggert organizing so far)
• Use synergy for e.g. simulation, physics
  studies forward detector studies.
• Common DAQ/Trigger for CMS TOTEM
• Discussions on T2
• Common simulation etc
• Share physics studies
• CMS has now officially a diffractive physics
  program/group, using CMS
• TOTEM detectors. Both experiments open to
  new collaborators
• ? Common LOI on diffractive physics on the
  time scale of 1 year
• ? Chapter in the CMS physics TDR
• ? MOU between CMS/TOTEM being prepared for
  complete detector runs
• ATLAS RPs for luminosity measurement/Diffraction
  to be considered later

CMS/TOTEM is the largest acceptance detector ever
built at a hadron collider
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CMS interests under discussion/LOI projects

• CMS central detector
• Diffractive Gap Trigger (being studied)
• T2 region
• Calorimeter (CASTOR)
• Add ? granularity (silicon, PPAC,) needs
  simulation studies
• Castor trigger
• So far one side of CMS (500 kCHF), additional
  funds requested
• T2 tracker (part of TOTEM, see TDR, GEM is
  baseline choice)
• May need participation from CMS esp. if silicon
  option would be chosen
• May need new tracker by CMS depends on TOTEM
  prototype results
• Roman pot detectors up to 220 m
• Use TOTEM RPs, available as a CMS subdetector
  (usable at low ?? check)
• Roman pot detectors at 300/400 m
• Completely new project
• Needs new resources (interest in CMS ATLAS)
• ZDC Zero Degree Calorimeter
  funding still under discussion
• New detectors in the range 7lt?lt9??? (20 m
  from IP) activity starting
• ? Certainly help welcome on simulation
  tools, detailed physics studies

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Summary Detecting Exclusive Higgs _at_ LHC

• Physics Case Can we expect to see a good signal
  over background?
• ? Signal understood (cross section) ?
  Uncertainty?
• ? Understanding of the background
  (inclusive/simulations!) started!
• ? compilation of the physics case being
  written up (BC,ADR, VK, J. Ellis)
• Can we detected the protons before 220 m? ? needs
  task force!
• Trigger for 300/400 RPs
• signals arrive too late for the trigger ? Can we
  trigger with the central detector only for L1.
  Not yet settled but there is hope
• Machine
• Can detectors be integrated in the cryostat ?
  needs task force!
• Which detector technologies? Mechanics? Risk
  analysis? ? needs studies
• Allignment, stability, access, radiation, etc
  need to be addressed

? Exciting
opportunity!! Lots of communalities
Experiments can work together! Likely to need
common ATLAS CMS/TOTEM effort to convince LHCC
But it will be a LHC phase-II project
(how soon?)