Central Higgs Production at LHC from SinglePomeronExchange

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Central Higgs Production at LHC from
Single-Pomeron-Exchange
S. Erhan, P.E. Schlein (UCLA) V.T. Kim
(Gatchina) hep-ph/0312342
Evidence for colorless gluon clusters
(Pomerons) in the proton UA8 (CERN)
observed jets in pp pX partonic structure H1
(DESY) ?p collisions show dominant (80-90)
gluonic structure of these clusters. Here, we
study Higgs production at LHC in pp p
(HX).
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UA8 pp (dijet X) p at 630 GeV
Et gt 8 GeV
A. Brandt et al., Phys. Lett B 297 (1992) 417.
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?-dependence in Flux Factor
The most likely Pomeron momentum
fraction is near zero. The Regge-pole
description of exchange process is FP/p(?,t)
x1-2a(t) where ?(t) 1 ? ? t At
fixed-t, FP/p(?) 1/xn
1 - ?
Experimentally, ?(t) is not a fixed Regge
trajectory. ? and ? depend on energy in pp
interactions and are different in ep interaction.
At t0, n 1.06 - 1.32
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Empirical evidence for gluon-clusters
Diffractive processes occur because of the
existence of colorless gluon-dominant clusters
(for example, digluons) in the partonic sea of a
proton which interact with the other beam proton.
There is now very solid empirical evidence for
the existence of such clusters. UA8 (CERN)
observed jets in pp pX, demonstrating the
partonic structure of the clusters and their very
hard internal structure (Super-Hard) H1 (DESY)
studied high-Q2 ?p collisions and showed the
dominant gluon structure of these clusters.
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LHC Kinematics of pp --gt p (H Y)
?1 ?2
MH2 ?1 ?2 s
xH ?1 - ?2
Assume ?1 comes from intermediate Pomeron
?1 ? ?
MH2
xH ? ? -
? ? s
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UA8 Feynman-x of dijet in Pp c.m.
Pomeron is Super-Hard. 30 of events have
x(2-jet) larger than predicted by the hard
structure function (1-x).
(b) Shows prediction when 1 gluon has entire
Pomeron mom.
x(2-jet)
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3 possible Pom. structure functions
Soft ? Fg/P(?) 6 (1 - ?)5 Hard ?
Fg/P(?) 6 ? (1 - ?)1 Super-Hard ? Fg/P(?)
0.7 6 ? (1 - ?) 0.3 19.8 ?8 (1-
?)0.3 Momentum sum rule is assumed. The
constituents of the Pomeron carry all its momentum
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Higgs cross section in Pp collisions
Ingelman and PS, Phys. Lett. 1985
where
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Higgs P(longitudinal) in Pom-prot c.m.
As in UA8 dijet analysis, the hard Pomeron causes
the Higgs to emerge in the Pomeron hemisphere.
Dijet analysis at LHC will quickly lead to the
best knowledge of Pomeron structure and its Q2
evolution.
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Higgs P(long.) in lab for 4 Mx values
The kinematic correlation between Mx and Higgs
P(longitudinal) provides an additional background
suppression tool. Select Mx bin and the
corresponding P(long.) bin which selects most of
Higgs signal.
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pp -gt p(HX) cross section vs. Mx
Cross section for 120 GeV mass Higgs depends very
weakly on ? in the range 0 to 0.1 (only by a
factor of two.).
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Total SPE Higgs cross section, 2 arms
SPE rate 7-9 of total What about dijets
? ?(dijets) 19nb (40 GeV) ?(dijets)
11nb (50 GeV) ?(dijets) 7nb (60 GeV)
Etmin
Integrated luminosity of 1036 will yield 11,000
dijets with Et gt 50 GeV. (uncertainty factor 2-3)
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All Higgs P(long.) in lab LHC TeV.
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Conclusions
1. Higgs production dominantly central. PYTHIA
studies are underway. TOTEM will suppress
bknd. 2. Dijet studies at the young LHC will
greatly contribute to better understanding the
Pomeron. Longitudinal dijet momentum
distributions in the Pomeron-proton cm lead to
Pomeron structure. 3. Measure ?
??(pp-gtp dijet)
K??(Pp-gtp dijet)

??(pp-gtp X)
K??(Pp-gtp X)
Over all xi and t. Extract upper right and
compare with prediction to determine K. UA8
found K 0.5 Donnachie-Landshoff value of 0.78
GeV-2
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Higgs detection background
Assertion Although certain types of background
are irreducible, for example gg bb, a general
reduction of hadronic activity in the final state
must improve Higgs detection and isolation
capability. In a typical LHC interaction, in
which a 120 GeV Higgs boson is produced, a gluon
participating in the fusion process has only
about 1 of the 7 TeV beam energy. But, in
Pomeron-exchange processes (diffraction), most
of the excess beam energy is carried away by a
single proton on one or both sides of the
interaction, thereby lowering the general
hadronic activity.