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Exclusive Higgs signals at the LHC. SM Higgs detection at the LHC inclusive signals – a brief review exclusive diffractive signals pp  p + H + p calculation of H bb bar signal and background Exclusive SUSY Higgs signals Calibration processes at the Tevatron

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slide1
Exclusive Higgs signals at the LHC
  • SM Higgs detection at the LHC

inclusive signals – a brief review

exclusive diffractive signals pp  p + H + p

calculation of H bbbar signal and background

  • Exclusive SUSY Higgs signals
  • Calibration processes at the Tevatron

pp  p + dijet +p, pp  p + gg + p

Alan Martin (IPPP,Durham)

slide6
A low mass Higgs (<130 GeV) will challenging

to identify

Hbb is dominant decay, but is swamped by

the QCD background

Best chance is Hgg

even though BR(Hgg) ~ 2. 10-3

slide8
conventional

signal for SM

110-130 GeV Higgs

slide9
All plots are normalized to an integrated luminosity of 1 fb-1 and the signal is scaled by a factor 10
  • Fraction of signal is very small (signal/background ~0.1)
slide13
exclusive Higgs production at the LHC

If the outgoing forward protons are measured

far from the interaction point then it is possible

to identify the Higgs and to make an accurate measurement of the

missing mass = MH

p

H

p

…but we must calculate the price for rapidity gaps ?

slide14
pp p + H + p

Khoze, Martin, Ryskin

If outgoing protons are tagged far from IP then s(M) = 1 GeV

(mass also from H decay products)

Very clean environment

Hbb: QCD bb bkgd suppressed by Jz=0 selection rule

S/B~1 for SM Higgs M < 140 GeV

L(LHC)~60 fb-1~10 observable evts after cuts+effic

Also HWW (L1 trigger OK) and Htt promising

SUSY Higgs: parameter regions with larger signal S/B~10,

even regions where conv. signal is challenging and

diffractive signal enhanced----h, H both observable

Azimuth angular distribution of tagged p’s spin-parity 0++

 FP420 --- letter of intent

slide16
no emission when (l ~ 1/kt) > (d ~ 1/Qt)

i.e. only emission withkt > Qt

slide17
calculated using detailed

2-channel eikonal global

analysis of soft pp data

S2 = 0.026 at LHC

S2 = 0.05 at Tevatron

Lonnblad

Monte Carlo

S2 = 0.026

S2 = 0.040

MH=120GeV

slide18
In summary, s(pp p + H + p)

contain Sudakov factor Tg which exponentially

suppresses infrared Qt region  pQCD

H

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

slide19
“enhanced”

correction

to sH(excl)?

eikonal

enhanced

S2 =0.026

KMR: using 2-channel eikonal

Gotsman,Levin,Maor..

Lonnblad, Sjodahl,

Bartels,Bondarenko,Kutak,Motyka

BBKMuse pert.thy.corrn could

be large and negative,

 s H(excl) reduced ?

KMR  small effect

slide20
Arguments why “enhanced” correction is small

KMR ‘06

DY threshold

Original Regge calc. required DY ~ 2-3 between Regge vertices

(Recall NLL BFKL:

 major part of all order resum has kinematic origin

 DY ~ 2.3 threshold implied by NLL  tames BFKL)

Applying to enhanced diagram

need 2DY > 4.6, but at LHC only

log(sqrt(s)/MH) available for yH=0

DY

DY

= 4.6 for MH=140 GeV

Higgs prod. via enhanced diagram

has v.tiny phase space at LHC

slide21
Background to ppp + (Hbb) + p signal

DKMOR

assuming DMmiss~3 GeV

LO (=0 if mb=0, forward protons)

B/S

gg  gg mimics gg  bb (P(g/b)=1%)

after polar angle cut 0.2

|Jz|=2 admixture (non-forward protons) 0.25

mb2/ET2 contribution <0.2

HO (gg)col.sing bb+ng

Still suppressed for soft emissions.

Hard emissions if g not seen:

extra gluon along beam Mmiss > Mbb 0

extra g from initial g along b or bbar 0.2

Pom-Pom inel. prod. B/S<0.5(DMbb/MPP)2 <0.004

for M=120 GeV 

total B/S~1

S~1/M3, B~DM/M6 : triggering, tagging, DM better with rising M

slide22
s(ppp+H+p) ~ 3 fb at the LHC

For LHC integrated L = 60 fb-1

after allowing for:

efficiency of the proton taggers

BR(Hbb)

b, b identification efficiency

polar angle cut

180 events  10 observable exclusive evts

with S/B~1

slide23
BSM: motivation for weak scale SUSY

Can stabilize hierarchy of mass scales: dMh2 ~ g2(mb2-mf2)

Gauge coupling unification (at high scale, but < Planck)

Provides a candidate for cold dark matter (LSP)

Could explain the baryon asymmetry of the Universe

SUSY effects at present energies only arise from loops--

so the SM works well

Provides an explanation for Higgs mechanism (heavy top)

The Higgs sector is the natural domain of SUSY. Higgs vev induced

as masses are run down from a more symmetric high scale

There must be a light Higgs boson, Mh < 140 GeV

slide24
SUSY Higgs: h, H, A, (H+, H--)

There are parameter regions where the exclusive

pp  p + (h,H) + p

signals are greatly enhanced in comparison to the SM

Selection rule favours 0++ diffractive production

slide27
Mh < 140

Mh in GeV

slide29
decoupling

regime:

mA ~ mH large

h = SM

intense coup:

mh ~ mA ~ mH

gg,WW.. coup.

suppressed

slide30
SM: pp  p + (Hbb) + p S/B~10/10~1

with DM = 3 GeV, at LHC with 60 fb-1

e.g. mA = 130 GeV, tan b = 50

(difficult for conventional detection,

but exclusive diffractive favourable)

S B

mh = 124.4 GeV 71 10 events

mH = 135.5 GeV 124 5

mA = 130 GeV 1 5

enhancement

slide31
exclusive signal

5s signal at LHC

30 fb-1

300 fb-1

slide32
Tasevsky et al

Diffractive: H bb

Yuk. coupling, DMH, 0++

5s

Inclusive:

H,A tt

wide bump

L=60 fb-1

mH=140

mH=160

motivation for cp violation in susy models
Motivation for CP-Violation in SUSY Models
  • In low energy SUSY, there are extra CP-violating phases beyond the CKM ones, associated with complex SUSY breaking parameters.
  • One of the most important consequences of CP-violation is its possible impact on the explanation of the matter-antimatter asymmetry.
  • Electroweak baryogenesis may be realized even in the simplest SUSY extension of the SM, but demands new sources of CP-violation associated with the third generation sector and/or the gaugino-Higgsino sector.
  • At tree-level, no CP-violating effects in the Higgs sector---CP violation appears at loop-level
slide34
CP violation in the Higgs sector

h, H, A mix  H1, H2, H3

mixing induced by

stop loop effects…

H1 could be light

Carena

slide35
Br.s in (fb) for H1, H2, H3 production at the LHC

fb

S/B~M5

cuts: (a) 60300 MeV, (c) 45

slide37
ppp + gg + p

KMR+Stirling

slide38
Measurements with Mgg=10-20 GeV

could confirm sH(excl) prediction

at LHC to about 20% or less

slide39
CDF II Preliminary

CDF Blessed this morning!

Albrow

3 events observed

16 events observed

It means exclusive H must happen

(if H exists) and probably ~ 10 fb

within factor ~ 2.5.

higher in MSSM

QED: LPAIR Monte Carlo

slide40
16 events were like this:

Albrow

3 events were like this:

slide41
Exptally more problematic due to

hadronization, jet algorithms, detector

resolution effects, QCD brem…

ppp + jj + p

Data plotted as fn. of Rjj = Mjj/MX, but above effects

smear out the expected peak at Rjj = 1(ExHuME MC)

Better variable:

Rj = (2ET cosh h*)/MX

highest ET jet h,ET

with h*=h-YM

Rj not changed by O(aS) final state radiation,

need only consider extra jet from initial state.

Prod.of other jets have negligible effect on Rj

due to strong ordering

We compute exclusive dijet and 3-jet prod

(and smear with Gaussian with resolution s=0.6/sqrt(ET in GeV))

slide42
ET>20GeV

Exclusive dijet and 3-jet prod

ET>20GeV

dijet

3-jet

dijets dominate Rj>0.8

3-jets dominate Rj<0.7

KMR, in prep.

Rj

slide43
Conclusion

The exclusive diffractive signal is alive and well.

The cross section predictions are robust.

Checks are starting to come from Tevatron data (gg,dijet…)

There is a very strong case for installing proton taggers

at the LHC, far from the IP ---- it is crucial to get the

missing mass DM of the Higgs as small as possible

The diffractive Higgs signals beautifully complement the

conventional signals. Indeed there are significant SUSY

Higgs regions where the diffractive signals are advantageous

---determining DMH, Yukawa Hbb coupling, 0++ determinn

---searching for CP-violation in the Higgs sector

slide45
Expect a depletion of

pp  p + bb + p

events as Rjj 1

slide46
KMR+Stirling

Diffractive c production

90

230

430

2000

9

20

50

130

only order-of-magnitude estimates possible for c production

slide47
Conclusions

Proton tagging is a valuable weapon in LHC Higgs physics

pp  p + (H bb) + p: S/B~1 if DMmiss~3 GeV, Mmiss = Mbb

especially for the important MH < 130 GeV region

SUSY Higgs: unique signals in certain domains of MSSM

tan b large (i) mh~mH~mA (s enhanced), (ii) mA large

Exclusive double diff. prod. strongly favours 0+

Azimuthal correlations are valuable spin-parity analyzer

Distinguish 0-- from 0+ Higgs

Possibility of detecting CP-violating Higgs

“standard candles” at Tevatron to test excl. prod. mechanism

ppp + c + p high rate, but only an ord.-of-mag.estimate

ppp + jj + p rate OK, but excl. evts have to be separated

ppp + gg + p low rate, but cleaner signal

slide49
Allow p’s to dissociate

Larger signal---but no sQCD(bb) suppression,

so use H1 tt (…) EiT>7 GeV

fb

p1T

j

p2T

1 + a sin 2j + b cos 2j if CP cons. then a=0, |b|=1

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