1.  MHV rule, (Super)Symmetries and ‘Diffractive Higgs’
QCD and High Energy Interactions La Thuile (Italy) , March  
MHV rule, (Super)Symmetries and ‘Diffractive Higgs’
V.A. Khoze (IPPP, Durham & PNPI)
Main aims • MHV rules and SUSY at the service of ‘diffractive Higgs’
• major QCD backgrounds to Hbb production at the LHC in the forward proton mode
(based on works with M.G. Ryskin, A.D. Martin and W.J. Stirling)
Higgs sector study- one of the central targets of FP420 physics menu
ADR
(X. Rouby)

2. Lack of : p p RG X RG p p  High -pt signatures in the central region
The LHC is a discovery machine !
CMS & ATLAS were designed and optimised to look beyond the SM
 High -pt signatures in the central region
But…
Main physics ‘goes Forward’
Difficult background conditions, pattern recognition, Pile Up...
The precision measurements are limited by systematics
(luminosity goal of δL ≤5% , machine ~10%)
Lack of :
Threshold scanning , resolution of nearly degenerate states
(e.g. MSSM Higgs sector)
Quantum number analysing
Handle on CP-violating effects in the Higgs sector
Photon – photon reactions , …
The LHC is a very challenging machine!
The LHC is not a precision machine (yet) !
ILC/CLIC chartered territory p p RG
Is there a way out? X
YES  Forward Proton Tagging
Rapidity Gaps  Hadron Free Zones
matching Δ Mx ~ δM (Missing Mass) RG p p
(X. Rouby)

3. Forward Proton Mode- Main Advantages for Higgs studies:
For theoretical audience
For experimental audience
MHV rules, Super (symmetry) and
‘Diffractive Higgs’ at the LHC
Irreducible Physics Backgrounds to
Diffractive Higgs Production
at the LHC
(K.G)
Forward Proton Mode- Main Advantages for Higgs studies:
• Measurement of the Higgs mass via the missing mass technique (irrespectively of the decay channel)
•Direct H bb mode opens up (Hbb Yukawa coupling);
unique signature for the MSSM Higgs sector.
•Quantum number/CP filter/analyzer
•Cleanness of the events in the central detectors.

4. -4 (CDPE) ~ 10  (incl) (A.Dechambre) (Khoze-Martin-Ryskin 1997-2008)
New CDF Excl. dijet results: A killing blow to the wide range of theoretical models.
not so long ago: between Scylla and Charibdis:
orders of magnitude differences in the theoretical predictions are now a history

5. situation in the MSSM is very different
Studying the MSSM Higgs Sector
without ‘clever hardware’:
for H(SM)bb at 60fb-1 only
a handful of events due to
severe exp. cuts and low efficiencies,
though S/B~1 .
But H->WW mode at M>135 GeV. (ADR,B.Cox et al-06)
 enhanced trigger strategy & improved timing detectors (FP420, TDR)
MSSM
situation in the MSSM is very different
from the SM
SM-like
>
Conventionally due to overwhelming QCD backgrounds, the direct measurement of Hbb is hopeless
The backgrounds to the diffractive H bb mode are
manageable!

6. For the channel bgds are well known and incorporated in the MCs:
some regions of the MSSM parameter space are especially proton tagging friendly
(at large tan  and M , S/B )
KKMR-04
HKRSTW, [hep-ph] B. Cox, F.Loebinger, A.Pilkington-07
Myths MC
For the channel bgds are well known and incorporated in the MCs:
Exclusive LO production (mass-suppressed) + gg misident+ soft & hard PP collisions.
Reality
The background calculations are still not fully complete:
(uncomfortably & unusually large high-order QCD and b-quark mass effects).
About a dozen various sources (studied by Durham group)
 admixture of |Jz|=2 production.
 NLO radiative contributions (hard blob and screened gluons)
 NNLO one-loop box diagram (mass- unsuppressed, cut-non-reconstructible)’
 ‘Central inelastic’ backgrounds (soft and hard Pomerons)
 b-quark mass effects in dijet events – still in progress
potentially, the largest source of theoretical uncertainties!
coming soon

7. for Higgs searches in the forward proton mode QCD backgrounds are suppressed
by Jz=0 selection rule and by colour, spin and mass resolution (M/M) –factors.
(KMR-2000)
There must be a god
Do not need many events to establish cleanly that the Higgs is a scalar and to measure
the mass

8. (D. Kosower)

9. NNLO
(CFCA)

11. Works is progress : W.J. Stirling et al, A. Shuvaev et al
Preliminary results of calculations with the SL accuracy- very promising:
a factor of 8 lower than the Born expectation (A. Shuvaev et al )
Good

12. (+ n soft gluons)

13. (angular brackets)

14. ‘Conventional’ MC algorithms cannot be used
kills soft gluon log
no collinear logs
‘Conventional’ MC algorithms cannot be used

15. 150 20 70 5 soft P 9 0.14 signal backgd hard P ds/dy|y=0 units 10-3 fb
SM (120 GeV) Higgs
signal
LO irreducible
backgd
hard P
150 20 70
X 1/8 5
soft P 9
0.14
ds/dy|y=0
units 10-3 fb
kT<5 GeV
DMdijet/Mbb=20%
DMmissing=4GeV

16.  Conclusion In some BSM scenarios pp p +(Hbb) +p may become a Higgs
Strongly suppressed and controllable QCD backgrounds in the forward proton
mode provide a potential for direct determination of the Hbb Yukawa coupling,
for probing Higgs CP properties and for measuring its mass and width.
In some BSM scenarios pp p +(Hbb) +p may become a Higgs
discovery channel at the LHC.
Further bgd reduction may be achieved by experimental improvements, better
accounting for the kinematical constraints, correlations…..
The complete background calculation is still in progress:
(unusually & uncomfortably large high-order QCD effects, Pile-Up at high lumi).
A clear downward tendency. 

17.  FP420, It is now or never Such opportunities come rarelyUK
Such opportunities come rarely
–let’s not waste this one!
FP420, It is now or never

18. 11. Thou shalt not delay, the LHC start-up is approaching.

19. BACKUP

20. A killing blow to the wide range of theoretical models.
Visualization of QCD Sudakov
formfactor
A killing blow to the wide range of theoretical models. d

22.  radiation from the screening gluon with pt~Qt :
 beam direction case
if a gluon jet is to go unobserved outside the CD or FD ( )
violation of the equality : (limited by the )
contribution is smaller than the admixture of Jz=2. KRS-06
b-direction case (HCA)
0.2 ( R/0.5)²
(R –separation cone size)
Note :  soft radiation factorizes  strongly suppressed is not a problem,
 NLLO bgd  numerically small
 radiation from the screening gluon with pt~Qt :
KMR-02
HC (Jz=2) LO ampt. ~ numerically very small
 hard radiation - power suppressed
MHV results for gg(Jz=0)ggg(g) amplitudes (dijet calibration, b-mistag)

23. Approximate formula for the background
main uncertn. at low masses
M- mass window over which we collect the signal
 b-jet angular cut : ( )
 both S and B should be multiplied by the overall ‘efficiency’ factor 
(combined effects of triggers, acceptances, exp. cuts, tagging efficienc., ….),
 ~4.2 % (120 GeV)
 g/b- misident. prob. P(g/b)=1.3% (ATLAS)
Four major bgd sources ~ (1/4 +1/4 + (1.3)²/4 + 1/2 ) at M≈120 GeV, M= 4GeV

26. mb=0