Diffractive Higgs Boson Photoproduction by Double

Diﬀractive Higgs boson photoproduction by Double Pomeron Exchange 1/ 12

Diﬀractive Higgs boson photoproduction by Double Pomeron Exchange

G.G. Silveira, M.B. Gay Ducati [email protected]

Grupo de Fenomenologia de Part´ıculas de Altas Energias Instituto de F´ısica Universidade Federal do Rio Grande do Sul Porto Alegre, RS, Brasil

G.G. Silveira, M.B. Gay Ducati XXVIII ENFPC — 24-28/set/2007 — Aguas´ de Lind´oia - SP Diﬀractive Higgs boson photoproduction by Double Pomeron Exchange 2/ 12 Motivations

I The existence of the Higgs boson is an open question in high energy Physics; I The Large Hadron Collider will allow to study a new kinematic region never before reached — √s = 14 TeV! I It is expected that the proton-proton collisions in LHC will be able to produce the Higgs boson.

I Collisions will occur with no strong interaction in LHC I The peripheral collisions are a new way to study the Higgs boson production in heavy-ion collisions.

I Other processes of Higgs production by DPE allow another way to study its production I DPE allows the Higgs boson production by the leading ggH vertex in the mass range MH = 100 200 GeV. − G.G. Silveira, M.B. Gay Ducati XXVIII ENFPC — 24-28/set/2007 — Aguas´ de Lindóia - SP Diffractive Higgs boson photoproduction by Double Pomeron Exchange 3/ 12 Diffractive Higgs production in pp collisions

I 1991: Bialas and Landshoﬀ PLB 256 (1991) 540

I Regge Theory non-perturbative gluons →

I 1997: Khoze, Martin and Ryskin PLB 401 (1997) 330

I QCD Pomeron two-gluons exchange →

p p p p IP H H IP p p p p

G.G. Silveira, M.B. Gay Ducati XXVIII ENFPC — 24-28/set/2007 — Aguas´ de Lind´oia - SP Diﬀractive Higgs boson photoproduction by Double Pomeron Exchange 4/ 12

Deeply Virtual Compton Scattering†

I 1998: γ∗p γp by Pomeron interaction in ep collisions →

γ∗ γ

p p

†Frankfurt, Freund, Strikman, PRD 58 (1998) 114001 G.G. Silveira, M.B. Gay Ducati XXVIII ENFPC — 24-28/set/2007 — Aguas´ de Lindóia - SP Diffractive Higgs boson photoproduction by Double Pomeron Exchange 5/ 12 Diffractive Higgs photoproduction

I Proposal: γp process by DPE in pp collision. q γ χac χb` γ q¯

2 pKfg (x,~k ) p

I The loop is treated in impact factor formalism at t = 0.

G.G. Silveira, M.B. Gay Ducati XXVIII ENFPC — 24-28/set/2007 — Aguas´ de Lind´oia - SP Diﬀractive Higgs boson photoproduction by Double Pomeron Exchange 6/ 12 Peripheral collisions

I The γp process is a subprocess in peripheral pp collisions

~b H

I Impact parameter: b > 2R NO STRONG INTERACTION! ⇒ I Only EM force acts on the second proton REAL PHOTONS ⇒ G.G. Silveira, M.B. Gay Ducati XXVIII ENFPC — 24-28/set/2007 — Aguas´ de Lind´oia - SP Diﬀractive Higgs boson photoproduction by Double Pomeron Exchange 7/ 12 Scattering amplitude I Partonic process: γq γ + H + q →

q(`µ) γ(qµ) γ(qµ) q¯(qµ `µ) − g(kµ) µ g(k ) CA Vh` H(qH ) g(kµ) q(pµ) q(pµ)

I The scattering amplitude is obtained by the Cutkosky Rules 2 2 ~ 2 1 20 MH αs α 2 αs CF dk Im A = d(PS)3 A(left) A(right) = s eq 2 9 Nc v π ~ 6 q k Z X Z ∗ ´ G.G. Silveira, M.B. Gay Ducati XXVIII ENFPC — 24-28/set/200| 7 —{zAguas} de Lind´oia - SP Diﬀractive Higgs boson photoproduction by Double Pomeron Exchange 8/ 12 Cross section for central rapidity

I The cross section is calculated for yH = 0

2 2 2 2 2 ∞ 2 d S M d~k ~2 2 σ gap H 4 2 2 −S(k ,MH ) 2 = αs α eq e fg (x, ~k ) 3 6 dyH y =0 18π b Nc v Q2 ~k H q ! "Z 0 # X

I 1 −1 → ~ 2 ~ 2 * Quark contribution : π αs CF fg (x, k ) = K ∂(`n ~k2) xg(x, k ) I 2 2 Gap Survival Probability : Sgap → 3% (5%) for LHC (Tevatron)

I 3 ~ 2 2 2 2 ~ 2 Gluon radiation supression : Sudakov factor S(k , MH ) ∼ `n MH /k I 2 Cutoff Q0 : Necessary to avoid infrared divergencies. I Electroweak vacuum expectation value: v = 246 GeV I pIP-vertex impact parameter: b = 5.5 GeV−2 1Khoze, Martin, Ryskin, EJPC 14 (2000) 525 2Khoze, Martin, Ryskin, EJPC 18 (2000) 167 3Forshaw, hep-ph/0508274 G.G. Silveira, M.B. Gay Ducati XXVIII ENFPC — 24-28/set/2007 — Aguas´ de Lindóia - SP Diffractive Higgs boson photoproduction by Double Pomeron Exchange 9/ 12 Results: pp vs. γp process

0,5

LHC :: E = 14 TeV Forshaw MRST2001lo Fotoprodução 2 2 0,4 Q 0 = 1.25 GeV

γp γ + H + p 0,3 → = 0) (fb) H (y H 0,2 /dy σ d

0,1 pp p + H + p → 0 60 80 100 120 140 160 180 200 MH (GeV) I Greatest event rate in the mass region expected for Higgs detection.

G.G. Silveira, M.B. Gay Ducati XXVIII ENFPC — 24-28/set/2007 — Aguas´ de Lind´oia - SP Diﬀractive Higgs boson photoproduction by Double Pomeron Exchange 10/ 12 Results: Gluon distribution functions

0,04 1,5 Tevatron :: E = 1.96 TeV MRST2001lo LHC :: E = 14 TeV MRST2001lo 2 2 MRST2004nlo 2 2 MRST2004nlo Q 0 = 1.00 GeV Q 0 = 1.00 GeV CTEQ6mE CTEQ6mE 1,25 0,03 ALEKHIN02lo ALEKHIN02lo

1 = 0) (fb) = 0) (fb) H 0,02 H 0,75 (y (y H H /dy /dy σ σ d d 0,5 0,01

0,25

0 0 200 400 600 800 1000 1200 1400 200 400 600 800 1000 1200 1400 MH (GeV) MH (GeV)

I Tevatron: Small diﬀerence between LO and NLO distributions;

I LHC: NLO distributions show a greater contribution than the LO ones.

G.G. Silveira, M.B. Gay Ducati XXVIII ENFPC — 24-28/set/2007 — Aguas´ de Lind´oia - SP Diﬀractive Higgs boson photoproduction by Double Pomeron Exchange 11/ 12 Results: Energy dependence

0,005

MRST2001lo 0,006 MH = 140 GeV 2 2 Q = 1.00 GeV 2 2 0 Q = 1.00 GeV 0,004 0 0,005

0,003 0,004 = 0) (fb) = 0) (fb) H H 0,003 (y (y H 0,002 H /dy /dy σ σ d d 0,002 MRST2001lo M = 120 GeV 0,001 H MRST2004nlo MH = 140 GeV 0,001 CTEQ6mE

MH = 180 GeV ALEKHIN02lo 0 0 5000 10000 15000 20000 5000 10000 15000 20000 E (GeV) E (GeV)

I Small dependence on Higgs mass;

I Aspect between the LO and NLO distributions:

I Same difference in the region √s = 9 17 TeV − include LHC region | {z } G.G. Silveira, M.B. Gay Ducati XXVIII ENFPC — 24-28/set/2007 — Aguas´ de Lindóia - SP Diffractive Higgs boson photoproduction by Double Pomeron Exchange 12/ 12 Summary

I Substantial results for Higgs boson production in γp process present in peripheral collisions; I An event rate three times bigger than the rate predicted by previous results in pp collisions; I Clear diﬀerence between LO and NLO distributions in the kinematic region of LHC; I Necessity of study the cross-section behavior in the very-high-energy limit; I Analysis of this production mechanism in pp collisions: Introduction of photon distribution in the proton; • I Include QCD and Electroweak theory corrections; I Predict physical observables for other production processes.

G.G. Silveira, M.B. Gay Ducati XXVIII ENFPC — 24-28/set/2007 — Aguas´ de Lind´oia - SP