6,002 research outputs found

### Measurements of Diffractive Processes at CDF

We review the results of measurements on hard diffractive processes performed
by the CDF Collaboration and report preliminary CDF results on two soft
diffractive processes with a leading antiproton and a rapidity gap in addition
to that associated with the antiproton. All results have been obtained from
data collected in Run I of the Fermilab Tevatron $\bar pp$ collider.Comment: 7 pages, Presented at 14$^{th}$ Topical Conference on Hadron Collider
Physics, HCP-2002, Karlsruhe, Germany, 29 Sep - 4 Oct 200

### Energy Level Diagrams for Black Hole Orbits

A spinning black hole with a much smaller black hole companion forms a
fundamental gravitational system, like a colossal classical analog to an atom.
In an appealing if imperfect analogy to atomic physics, this gravitational atom
can be understood through a discrete spectrum of periodic orbits. Exploiting a
correspondence between the set of periodic orbits and the set of rational
numbers, we are able to construct periodic tables of orbits and energy level
diagrams of the accessible states around black holes. We also present a closed
form expression for the rational q, thereby quantifying zoom-whirl behavior in
terms of spin, energy, and angular momentum. The black hole atom is not just a
theoretical construct, but corresponds to extant astrophysical systems
detectable by future gravitational wave observatories.Comment: 8 page

### Diffractive Higgs boson production at Tevatron and LHC: an experimental review

We discuss the different models of central diffractive production of the
Higgs boson at the Tevatron and the LHC. We also describe how the models can be
tested using diffractive production data being taken at the Tevatron. We
finally discuss the advantages of using diffractive events to reconstruct the
mass of the Higgs boson especially at the LHC.Comment: short review to be published in Mod. Phys. Let

### Triangular mass matrices for quarks and leptons

We assume that all quark and lepton $3 \times 3$ mass matrices which appear
in the standard model lagrangian (after spontaneous symmetry breaking) with
neutrinos treated as Dirac patricles have the triangular form. Such matrices
have not only less non-zero elements (three of them are equal to zero) but also
lead to very asymmetrical decomposition into one diagonal and two unitary
matrices for quarks and leptons. We also assume that unitary matrices which
transform flavor into definite mass states for right handed components (weakly
non-interacting) in the same weak isodoublet are equal. Using all available
experimental data on quark and lepton masses and mixing angles, treating in the
universal way quarks and leptons, we determine the triangular mass matrices for
up and down type quarks, neutrinos and charged leptons and as a consequence
mixing matrices for left-handed and right handed components. As the result of
the fit we get predictions for the neutrino masses including smallest neutrino
mass. The calculations without CP violation and with inclusion of this effect
in quark sector are also presented.Comment: 12 pages, no figure

### The Ratio of W + N jets To Z/gamma + N jets As a Precision Test of the Standard Model

We suggest replacing measurements of the individual cross-sections for the
production of W + N jets and Z/gamma + N jets in searches for new high-energy
phenomena at hadron colliders by the precision measurement of the ratios (W+0
jet)/(Z+0 jet), (W+1 jet)/(Z+1 jet), (W+2 jets)/(Z+2 jets),... (W+N jets)/(Z+N
jets), with N as large as 6 (the number of jets in ttbarH). These ratios can
also be formed for the case where one or more of the jets is tagged as a b or c
quark. Existing measurements of the individual cross sections for Wenu + N jets
at the Tevatron have systematic uncertainties that grow rapidly with N, being
dominated by uncertainties in the identification of jets and the jet energy
scale. These systematics, and also those associated with the luminosity, parton
distribution functions (PDF's), detector acceptance and efficiencies, and
systematics of jet finding and b-tagging, are expected to substantially cancel
in calculating the ratio of W to Z production in each N-jet channel, allowing a
greater sensitivity to new contributions in these channels in Run II at the
Tevatron and at the LHC.Comment: 10 pages, 8 figures, added reference

### On signals of new physics in global event properties in pp collisions in the TeV energy domain

In the framework of the weighted superposition mechanism of different classes
of minimum bias events (or substructures), described by the negative binomial
multiplicity distribution, in possible scenarios for pp collisions in the TeV
energy domain, we explore global properties of an eventual new class of events,
characterised by high hadron and clan densities, to be added to the soft
(without minijets) and semihard (with minijets) ones. It turns out that the
main signal of the mentioned new physical expectations at 14 TeV c.m. energy
would be an ``elbow structure'' in the tail of the total charged particle
multiplicity distribution in complete disagreement with the second shoulder
structure predicted by Pythia Monte Carlo calculations: a challenging problem
for new experimental work.Comment: 14 pages, 6 ps figures include

### Polarization of Upsilon(nS) at the Tevatron

The polarization of inclusive Upsilon(nS) at the Fermilab Tevatron is
calculated within the nonrelativistic QCD factorization framework. We use a
recent determination of the NRQCD matrix elements from fitting the CDF data on
bottomonium production from Run IB of the Tevatron. The result for the
polarization of Upsilon(1S) integrated over the transverse momentum bin 8 < p_T
< 20 GeV is consistent with a recent measurement by the CDF Collaboration. The
transverse polarization of Upsilon(1S) is predicted to increase steadily for
p_T greater than about 10 GeV. The Upsilon(2S) and Upsilon(3S) are predicted to
have significantly larger transverse polarizations than Upsilon(1S).Comment: 15 pages, 3 figure

### Squark Mixing in Electron-Positron Reactions

Squark mixing plays a large role in the phenomenology of the minimal
supersymmetric standard model, determining the mass of the lightest Higgs boson
and the electroweak interactions of the squarks themselves. We examine how
mixing may be investigated in high energy $e^+ e^-$ reactions, both at LEP-II
and the proposed linear collider. In particular, off-diagonal production of one
lighter and one heavier squark allows one to measure the squark mixing angle,
and would allow one to test the mass relations for the light Higgs boson. In
some cases off-diagonal production may provide the best prospects to discover
supersymmetry. In the context of the light bottom squark scenario, we show that
existing data from LEP-II should show definitive evidence for the heavier
bottom squark provided that its mass $m_{\tilde{b}_2} \le 120$ GeV.Comment: 22 pages, latex, 6 figure

### Heavy Flavours in Collider Experiments

Current issues in the studies of Heavy Flavours in colliders are described
with particular emphasis on experiments in which the UK is involved. Results on
charm production at HERA are examined and compared to those at the Tevatron. B
production rates at the Tevatron as well as the status of B lifetimes and
mixing in the LEP collaborations and at the Tevatron are highlighted. The
measurement of sin2beta from CDF is described as well as the most recent
results on top physics at the Tevatron

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