MPI, Nov. 2006. Diffractive processes as a tool for testing the MSSM Higgs sector at the LHC. ( a theorist’s view ). V.A. K hoze (IPPP, Durham). main aim: to show that the Central Diffractive Processes may provide an exceptionally clean environment to search
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Diffractive processes as a tool for testing the MSSM Higgs sector at the LHC
(a theorist’s view)
V.A. Khoze (IPPP, Durham)
main aim:to show that the Central Diffractive Processes
may provide an exceptionally clean environment to search
for and to identify the nature of new physics at the LHC
The LHC will be a very challenging machine!
Is there a way out?
☺YES-> Forward Proton Tagging
Rapidity Gaps Hadron Free Zones
matchingΔ Mx ~δM (Missing Mass)
Higgs is only a part of the broad EW, BSM and [email protected]
wealth of QCD studies, glue-glue collider, photon-hadron, photon-photon interactions…
FPT will open upan additional richphysics menu [email protected]
LHC as a High Energy gg Collider
K. Piotrzkowski, Phys. Rev. D63 (2001) 071502(R)
J.Ohnemus, T.Walsh & P .Zerwas -94;
Very rich Physics Menu
The basic ingredients of the KMRapproach(Khoze-Martin-Ryskin 1997-2006)
Interplay between the soft and hard dynamics
RGsignature for Higgs hunting(Dokshitzer, Khoze, Troyan, 1987). Developed and promoted by Bjorken (1992-93)
(CDPE) ~ 10 * (incl)
High price to pay for such a clean environment:
σ (CEDP) ~ 10
Rapidity Gapsshould survive hostilehadronicradiation
damagesand ‘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
the same for Signal and Bgds
contain Sudakov factor Tg which exponentially suppresses infrared Qt region pQCD
new CDF experimental confirmation, 2006
S² is the prob. that the rapidity gaps survive population
by secondary hadrons soft physics; S²=0.026(LHC),
S²/b² -weak dependenceonb.
LHC : ‘after discovery stage’,Higgs ID……
How do we know what we’ve found?
mass, spin, couplings to fermions and Gauge Bosons, invisible modes…
for all these purposes the CEDP will be particularly handy !
Measure the Higgs mass via the missing mass technique
Mass measurements do not involve Higgs decay products
Cleanness of the events in the central detectors.
Tagging the leading protons
Selection of exclusive events & backgrounds, PU -events
Triggering at L1 in the LHC experiments.
bb-mode requires special attention.
Uncertainties in the theory
(Unusually& uncomfortably) large higher-order effects,
model dependence of predictions (soft hadronic physics is involved after all)
There is still a lot to learn from present and future Tevatron diffractive data (KKMRS- friendly so far).
The MSSM and more exotic scenarios
If the coupling of the Higgs-like object to gluons is large, double proton tagging becomes very attractive
(E.Boos et al, 02-03)
Potentially of great importance for electroweak baryogenesis
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)
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)
a ‘simplest’ extension of the minimal Higgs sector
(h SM-like, H/A- degenerate.)
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
0++ selection rule suppresses A production:
CEDP ‘filters out’ pseudoscalar production, leaving pure H sample for study
Well known difficult region for conventional channels, tagged proton channel may well be thediscovery channel,and is certainly a powerful spin/parity filter
mA ~ mH150GeV,
h = SM
mh ~ mA ~ mH
With CEDP the mass range up to 160-170 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
( S.Heinemeyer, V.A. Khoze , W.J.Stirling, M. Ryskin, ,M. Tasevsky and G. Weiglein )
mhmax scenario, =200 GeV, MSUSY =1000 GeV
mh 121-123 GeV
for the SM Higgs
at M = 120 GeV = 0.4 fb,
at M= 140 GeV = 1 fb
Hunting the CP-odd boson, A
(LO)selection rule – an attractive feature of the CEDPprocesses, but……
the flip side to this coin:
strong ( factor of ~ 10² )suppression of the CED production of the A boson.
A way out : to allow incoming protons to dissociate(E-flowET>10-20 GeV)KKMR-04
pp p + X +H/A +Y +p(CDD)
in LO azim. angular dependence: cos² (H), sin² (A), bkgd- flat
A testing ground for CP-violation studies in the CDD processes (KMR-04)
challenges: bb mode – bkgd conditions -mode- small (QED)bkgd, but low Br
…the LHC as a ‘gluino factory’ , N. Arkani-Hamed( Pheno-05)
New studies: Manchester Group
pp pp + ‘nothing’
further progress depends on the survival ….
various potential problems of theFPTapproach reveal themselves
however there is a (good) chance to observe such an invisible object,
which, otherwise, may have to await aILC
searches for extra dimensions – diphoton production(KMR-02)
BREAKING NEWS, CDF
First experimental results are encouraging, new data are underway
….a lot of new exciting plots to come…
dN/dhTevatron vs HERA:Factorization Breakdown
1. Thoushalt not worship any other god but the First Principles,
and even ifthoulikest it not, go by thyBook.
2. Thou slalt not make untotheeanygraven image,
thou shalt not bow down thyself to them .
3.Thou shalttreat the existing diffractive experimental
data in ways that show great consideration and respect.
4.Thou shalt drawthy daily guidance from the standard
candleprocesses for testing thy theoretical models.
5. Thou shalt remember the speed of light to keep it holy. (trigger latency)
6.Thou shalt notdishonour backgrounds and shaltstudy
them with great care.
7.Thou shaltnotforget about the pile-up (an invention ofSatan).
8.Though shalt notexceed the trigger thresholds and
the L1 saturation limit. Otherwise thy god shall surely punish thee forthyarrogance.
9.Thou shalt not annoy machine people.
10. Thou shalt not delay, the LHC start-up is approaching
Forward Proton Taggingwouldsignificantlyextend the physics reachof the ATLASand CMS detectors by giving access to a wide
range of exciting new physics channels.
FPT has the potential to make measurements which are unique at LHC and challenging even at a ILC.
For certain BSMscenarios theFPT may be the Higgs discoverychannel within the first three years of low luminosity running
FPT offers a sensitive probe of the CP structure of the
The R&D studies must be completed within 12 months
(only limited time-scale and manpower available)
R&D fully funded till middle of 2007
(first long break).
The LHC is coming!
Reliability of predn of s(pp p + H + p) crucial
contain Sudakov factor Tg which exponentially
suppresses infrared Qt region pQCD
S2 is the prob. that the rapidity gaps survive population by secondary hadrons soft physics S2=0.026 (LHC) S2=0.05 (Tevatron)
s(pp p + H + p) ~ 3 fb at LHC for SM 120 GeV Higgs
~0.2 fb at Tevatron
Current understanding of the bb backgrounds for CED production
for reference purposes SM (120 GeV)Higgsinterms of S/B ratio (various uncrt. cancel)
First detailed studies by De Roeck et al. (DKMRO-2002)
Preliminary results and guesstimates– work still in progress
S/B1 at ΔM 4 GeV
Four main sources (~1/4 each)
gluon-b misidentification (assumed 1% probability) Prospects to improve in the CEDP
environment ? Better for larger M.
NLO 3-jet contribution Correlations, optimization -to be studied.
admixture of |Jz|=2 contribution
b-quark mass effects in dijet events Further studies of the higher-order QCD
The complete background calculations are still in progress
(unusually large high-order QCD and b-quark mass effects).
Optimization, MC simulation- still to be done
Mass dependence of theSM(CEDP):SH~1/M³
Bkgd :ΔM/Mfor ,
( ΔM ,triggering, tagging etc improving with rising M)
Azimuthal asymmetry in tagged protons provides direct evidence for CP violation in Higgs sector
‘CPX’ scenario ( in fb)
A is practically uPDF - independent
CP odd active at non-zero t
Results in tri-mixing scenaio (J.Ellis et al) are encouraging,
(KMR in progress)