1. Diffractive Processes as a Tool to Study
New Physics at the LHC

2. ☺ YES-> Forward Proton Tagging
CMS & ATLAS were designed and optimised to look beyond the SM
 High -pt signatures in the central region
But… incomplete
Main physics ‘goes Forward’
Difficult background conditions.
The precision measurements are limited by systematics
(luminosity goal of δL ≤5%)
 Lack of :
Threshold scanning
ILC chartered territory
Quantum number analysing
Handle on CP-violating effects in the Higgs sector
Photon – photon reactions p p p RG
Is there a way out?
☺ YES-> Forward Proton Tagging
Rapidity Gaps  Hadron Free Zones
Δ Mx ~ δM (Missing Mass) X RG p p

3. R. Orava, ISMD-05
recall bj’s idea of FAD

4. (a gluonic Aladdin’s lamp)
PLAN
1. Introduction
(a gluonic Aladdin’s lamp)
2.Basic elements of KMR approach
(a qualitative guide)
3. Prospects for CED Higgs production.
the SM case
MSSM Higgses in the troublesome regions
MSSM with CP-violation
‘Exotics’
5. Conclusion
6. Ten commandments of Physics with
Forward Protons at the LHC .

5. Forward Proton Taggers as a gluonic Aladdin’s Lamp
(Old and New Physics menu)
Higgs Hunting (the LHC ‘core business’) K(KMR)S
Photon-Photon, Photon - Hadron Physics
‘Threshold Scan’: ‘Light’ SUSY KMR-02
Various aspects of Diffractive Physics (soft & hard ). KMR-01
(strong interest from cosmic rays people )
Luminometry KMOR-01
High intensity Gluon Factory. KMR-00, KMR-01
QCD test reactions, dijet luminosity monitor
Searches for new heavy gluophilic states KMR-02
FPT
☻ Would provide a unique additional tool to complement the conventional strategies at the LHC and ILC.
 Higgs is only a part of a broad diffractive
a wealth of QCD studies , photon-hadron interactions…
FPT  an additional physics menu in

6. The basic ingredients of the KMR approach (1997-2005)
Interplay between the soft and hard dynamics
RG signature for Higgs hunting ( Dokshitzer, Khoze, Troyan, 1987)
Sudakov
suppression
Bialas-Landshoff rescattering/absorptive
( Born -level ) effects
Main requirements:
inelastically scattered protons remain intact
active gluons do not radiate in the course of evolution up to the scale M
<Qt> >>/\QCD in order to go by pQCD book -4
(CDPE) ~ 10 * (incl)

7. σ (CEDP) ~ 10 σ( inclus.) H P P W = S² T² -4
High price to pay for such a clean environment:
σ (CEDP) ~ 10 -4
σ( inclus.)
Rapidity Gaps should survive hostile hadronic radiation
damages and ‘partonic pile-up ‘
W = S² T²
Colour charges of the ‘digluon dipole’ are screened
only at rd ≥ 1/ (Qt)ch
GAP Keepers (Survival Factors) , protecting RG against:
the debris of QCD radiation with 1/Qt≥ ≥ 1/M (T)
soft rescattering effects (necessitated by unitariy) (S)
How would you explain it to your (grand) children ?
Forcing two (inflatable) camels to go through the eye
of a needle H P P

8. (x’~Qt/√s) <<(x~ M/√s) <<1
schematically
skewed unintegrated structure functions (suPDF)
(x’~Qt/√s) <<(x~ M/√s) <<1
(Rg=1.2 at LHC)
T(Qt,μ) is the probability that a gluon Qt remains untouched in the evolution up to the hard scale M/2
T + anom .dim. → IR filter
( the apparent divergency in the Qt integration nullifies)
<Qt>SP~M/2exp(-1/αs), αs =Nc/π αs Cγ
SM Higgs, <Qt>SP ≈ 2 GeV>> ΛQCD

9. An important role of subleading terms in fg(x,x’,Qt²,μ²),
MAIN FEATURES
An important role of subleading terms in fg(x,x’,Qt²,μ²),
(SL –accuracy).
Cross sections σ~ (fg ) ( PDF-democracy)
S² KMR=0.026 (± 50%) SM Higgs at LHC
(detailed two-channel eikonal analysis of soft pp data)
good agreement with all other groups and MC.
S²/b² - quite stable (within 10-15%) KMR(S)
S²~ s (Tevatron-LHC range)
dL/d(logM² ) ~ 1/ (16+ M)
a drastic role of Sudakov suppression (~ 1/M³)
σH ~ 1/M³ , (σB) ch ~ Δ M/ M 4 ^ ^
(GLM, M.Bloch et al, M. Strikman et al, V.Petrov et al.) ^ ^
-016
3.3 6
Jz=0 ,even P- selection rule for σ is justified
only if <pt>² /<Qt>² « 1

10. Central Exclusive Production of a New Heavy State M
We shouldn’t underestimate photon fusion !

11. Higgs boson
LHC cost
REWARD
2.5 billion

12. Current consensus on the LHC Higgs search prospects
SM Higgs : detection is in principle guaranteed ☺
for any mass.
In the MSSM h-boson most probably cannot ☺
escape detection ,and in large areas
of parameter space other Higgses can be found.
But there are still troublesome areas of the 
parameter space:
intense coupling regime of MSSM, MSSM with CP-violation…..
More surprises may arise in other SUSY
non-minimal extensions : NMSSM….
After discovery stage (Higgs identification):
Common strategy:
The ambitious program of precise measurements of the H mass, width, couplings, and, especially of the quantum numbers and
CP properties would require an interplay
with a ILC

13. ~4 GeV(currently feasible) Valuable quantum number filter/analyser.
The advantages of CED Higgs production
Prospects for high accuracy mass measurements
( ΓH and even lineshape in some MSSM scenarios)
mass window M = 3 ~ 1 GeV (the wishlist)
~4 GeV(currently feasible)
Valuable quantum number filter/analyser.
( 0++ dominance ;C , P-even)
 difficult or even impossible to explore the light Higgs CP at the LHC conventionally.
(an important ingredient of pQCD approach,
otherwise, large |Jz|=2 …effects, ~(pt/Qt)2 !)
H ->bb, especially at large tanβ
(gg)CED  bb LO (NLO,NNLO) BG’s -> studied
SM Higgs S/B~3(1GeV/M)
complimentary information to the conventional studies( also ՇՇ)
H →WW*/WW - an added value
especially for SM Higgs with M≥ 135GeV, MSSM,
small eff ‘benchmark’ MSSM scenario
New leverage –proton momentum correlations
(probes of QCD dynamics, pseudoscalar ID,
CP violation effects) KMR-02

14. Exclusive SM Higgs production
b jets : MH = 120 GeV s = 2 fb (uncertainty factor ~2.5)
MH = 140 GeV s = 0.7 fb
MH = 120 GeV : 10 signal / O(10) background
in 30 fb-1
(with detector cuts)
(optimistic, but not inconceivable) H
WW* : MH = 120 GeV s = 0.4 fb
MH = 140 GeV s = 1 fb
MH = 140 GeV : 5-6 signal / O(3) background in 30 fb-1
(with detector cuts)
The b jet channel is possible, with a good understanding of detectors and clever level 1 trigger.
The WW channel is extremely promising : no trigger problems, better mass resolution at higher masses (even in leptonic / semi- leptonic channel), weaker dependence on jet finding algorithms
If we see SM-like Higgs + p- tags  the quantum numbers are 0++ H

15. ☺ An added value of the WW channel
1. ‘less demanding’ experimentally
(trigger and mass resolution requirements..)
allows to avoid the potentially difficult issue of triggering
on the low pt-jets
2. higher acceptances and efficiencies
3. an extension of well elaborated conventional program,
(existing experience, MC’s…)
4. the decrease in the cross section is compensated for
by the increasing Br and increased detection efficiency
5. missing mass resolution improves as MH increases
6. the mass measurement is independent of the decay products of the central system
7. Better quantitative understanding of backgrounds.
Very low backgrounds at high mass.
assignment and spin-parity analyzing power
still hold
☻good prospects to double the signal rate (trigger thresholds)
☻ small eff MSSM benchmark scenario – (factor of ~4)

16. The MSSM and more exotic scenarios
If the coupling of the Higgs-like object to gluons is large, double proton tagging becomes very attractive
The intense coupling regime of the MSSM
(E.Boos et al, 02-03)
CP-violating MSSM Higgs physics (A.Pilaftsis,98; M.Carena et al.,00-03, B.Cox et al 03, KMR-03, J. Ellis et al -05)
Potentially of great importance for electroweak baryogenesis
an ‘Invisible’ Higgs (BKMR-04)
NMSSM ( with J. Gunion et al in progress)

17. MA ≤ 120-150GeV, tan β >>1 ( E.Boos et al,02-03)
(a )The intense coupling regime
MA ≤ GeV, tan β >>1 ( E.Boos et al,02-03)
h,H,A- light, practically degenerate
large Γ, must be accounted for
the ‘standard’ modes WW*,ZZ*, γγ …-strongly suppressed v.s. SM
maybe, the best bet – μμ -channel,
in the same time – especially advantageous for CEDP: ☺
(KKMR 03-04)
σ(gg ->Higgs)Br(Higgs->bb) - significantly exceeds SM.
thus, much larger rates.
Γh/H ~ ΔM,
0- is filtered out, and the h/H separation may
be possible
(b) The intermediate regime: MA ≤ 500 GeV,
tan β <
(the LHC wedge, windows)
(c) The decoupling regime
MA>> 2MZ (in reality, MA>140 GeV, tan β>10)
h is SM-like, H/A -heavy and approximately degenerate,
CEDP may allow to filter A out

18. The MSSM can be very proton tagging friendly
The intense coupling regime is where the masses of the 3 neutral Higgs bosons are close to each other and tan  is large
suppressed
enhanced
0++ selection rule suppresses A production:
CEDP ‘filters out’ pseudoscalar production, leaving pure H sample for study
MA = 130 GeV, tan = 50
Mh = 124 GeV :71signal / (3-9) background in 30 fb-1
MH = 135 GeV : 124 signal / (2-6) background in 30 fb-1
MA = 130 GeV : 3 signal / (2-6) background in 30 fb-1
for 5 ϭ BR(bb) > 0.7fb (2.7fb) for 300 (30fb-1)
Well known difficult region for conventional channels, tagged proton channel may well be the discovery channel, and is certainly a powerful spin/parity filter

19. clearly distinguishable
decoupling regime:
mA ~ mH large
h = SM
intense coupl:
mh ~ mA ~ mH
,WW.. coupl
suppressed
with CEDP:
h,H may be
clearly distinguishable
outside130+-5
GeV range,
h,H widths are quite different

20. Helping to cover the LHC gap?
With CEDP the mass range up to GeV can be covered at medium tan and up to 250 GeV for very high tan , with 300 fb-1
Needs ,however, still full simulation
pile-up ?

21. Azimuthal angle between the leaprotons depends on spin of H
Spin Parity Analysis
Azimuthal angle between the leading protons depends on spin of H
 angle between protons with
rescattering effects included
 angle between protons
Azimuthal angle between the leaprotons depends on spin of H
Measure the azimuthal angle of the proton on the proton taggers
KKMR -03

22. Probing CP violation in the Higgs Sector
Azimuthal asymmetry in tagged protons provides direct evidence for CP violation in Higgs sector
‘CPX’ scenario ( in fb)
KMR-04
A is practically uPDF - independent
CP odd active at non-zero t
CP even
Results in tri-mixing scenaio (J.Ellis et al) are encouraging

23. “lineshape analysis” J. Ellis et al. hep-ph/0502251 Scenario with CP
violation in the
Higgs sector and
tri-mixing

24. Summary of CEDP e.g. mA = 130 GeV, tan  = 50 L = 30 fb-1 S B
The missing mass method may provide unrivalled Higgs mass resolution
Real discovery potential in some scenarios
Very clean environment in which to identify the Higgs,for example, in the CPX or tri-mixing scenarios
Azimuthal asymmetries may allow direct measurement of CP violation in Higgs sector
Assuming CP conservation, any object seen with 2 tagged protons has positive C parity, is (most probably) 0+, and is a colour singlet
e.g. mA = 130 GeV, tan  = 50
L = 30 fb-1
S B
mh = GeV ~ 3 events
mH = GeV ~2
mA = GeV ~2 bb
X M
1 GeV
 WW*/WW modes are looking extremely attractive.
  mode looks quite promising

25. …the LHC as a ‘gluino factory’ , N. Arkani-Hamed ( Pheno-05)
BFK-92
KMR-02
pp  pp + ‘nothing’
further progress depends on the survival ….

26.  searches for extra dimension – diphoton production (KMR-02)
an ‘Invisible ‘ Higgs
KMR-04 H
several extensions of the SM: a fourth generation
some SUSY scenarios,
large extra dimensions
(one of the ‘LHC headaches’ )
the advantages of the CEDP – a sharp peak in the MM spectrum, mass determination, quantum numbers
strong requirements :
triggering directly on L1 on the proton taggers
low luminosity : L= 10 ³² -10 ³³ cm -2 sec (pile-up problem) ,
forward calorimeters (…ZDC) (QED radiation , soft DDD),
veto from the T1, T2- type detectors (background reduction, improving the trigger budget)
 various potential problems of the FPT approach reveal themselves
 however there is a (good) chance to observe such an invisible object,
which, otherwise, may have to await a ILC
 searches for extra dimension – diphoton production (KMR-02)

27. Still more work to be done to constrain the uncertainties
EXPERIMENTAL CHECKS
Up to now the diffractive production data are consistent with K(KMR)S results
Still more work to be done to constrain
the uncertainties
Very low rate of CED high-Et dijets;
observed yield of Central Inelastic dijets
(CDF, Run I, Run II) data up to (Et)min>50 GeV
‘Factorization breaking’ between the effective diffractive structure functions measured at the Tevatron and HERA.
(KKMR-01 ,a quantitative description of the results,
both in normalization and the shape of the
distribution)
The ratio of high Et dijets in production with one
and two rapidity gaps
Preliminary CDF results on exclusive charmonium
CEDP. Higher statistics is underway.
Energy dependence of the RG survival (D0, CDF)
CDP of γγ, breaking news

28. Tevatron vs HERA: Factorization Breakdown
dN/d
gap p IP
CDF H1 e *
t p
well

29. CDF-2000
KKMR-01
The measured CDF dijet diffractive distribution compared with KKMR predictions

30. “standard candles”
First experimental results are encouraging, new data are underway

31. CDF exclusive di-jet limits
H-mass range
KMR expectations

32. CHIC
DIS04
KMR-01,
70 pb
47 pb

33. pp  p + γγ + p
KMRS-04

34. KMRS-04

35. BREAKING NEWS

36. (KMR/ExHume)

38. CONCLUSION
Forward Proton Tagging would significantly extend the physics reach of the ATLAS
and CMS detectors by giving access to a wide
range of exciting new physics channels.
For certain BSM scenarios the FPT may be the Higgs discovery channel within the first
three years of low luminosity running
 FPT may provide a sensitive window into
CP-violation and new physics
 Nothing would happen before the experimentalists come FORWARD and do the REAL WORK
We (FP-420) must work hard here – there is no easy solution

39. FP420 LOI-submitted to the LHCC: CERN-LHCC-2005-025 LHCC-I-015
(68 authors, 29 institutes in 10 countries on both ATLAS and CMS)
LOI-submitted to the LHCC: CERN-LHCC LHCC-I-015
FP420 : An R&D Proposal to Investigate the Feasibility of Installing Proton Tagging Detectors in the 420m Region at LHC
From the LHCC minutes (October 2005)
The LHCC heard a report from the FP420 referee. In its Letter of Intent,the FP420 Collaboration puts forward an R&D proposal to investigate the feasibility of installing proton tagging detectors in the 420 m. region at the LHC. By tagging both outgoing protons at 420 m. a varied QCD,electroweak, Higgs and Beyond the Standard Model physics programme becomes accessible. A prerequisite for the FP420 project is to assess the feasibility of replacing the 420 m. interconnection cryostat to facilitate access to the beam pipes and therefore allow proton tagging detectors to be installed.
The LHCC acknowledges the scientific merit of the FP420 physics programme and the interest in its exploring its feasibility.