586 research outputs found
Jets in Hadron-Hadron Collisions
In this article, we review some of the complexities of jet algorithms and of
the resultant comparisons of data to theory. We review the extensive experience
with jet measurements at the Tevatron, the extrapolation of this acquired
wisdom to the LHC and the differences between the Tevatron and LHC
environments. We also describe a framework (SpartyJet) for the convenient
comparison of results using different jet algorithms.Comment: 68 pages, 54 figure
Understanding the newly observed Y(4008) by Belle
Very recently a new enhancement around 4.05 GeV was observed by Belle
experiment. In this short note, we discuss some possible assignments for this
enhancement, i.e. and molecular state. In these two
assignments, Y(4008) can decay into with comparable
branching ratio with that of . Thus one suggests
high energy experimentalists to look for Y(4008) in channel.
Furthermore one proposes further experiments to search missing channel
, and especially and
, which will be helpful to distinguish and
molecular state assignments for this new enhancement.Comment: 4 pages, 5 figures. Typos correcte
Maverick dark matter at colliders
Assuming that dark matter is a weakly interacting massive particle (WIMP)
species X produced in the early Universe as a cold thermal relic, we study the
collider signal of pp or ppbar -> XXbar + jets and its distinguishability from
standard-model background processes associated with jets and missing energy. We
assume that the WIMP is the sole particle related to dark matter within reach
of the LHC--a "maverick" particle--and that it couples to quarks through a
higher dimensional contact interaction. We simulate the WIMP final-state signal
XXbar + jet and dominant standard-model (SM) background processes and find that
the dark-matter production process results in higher energies for the colored
final state partons than do the standard-model background processes, resulting
in more QCD radiation and a higher jet multiplicity. As a consequence, the
detectable signature of maverick dark matter is an excess over standard-model
expectations of events consisting of large missing transverse energy, together
with large leading jet transverse momentum and scalar sum of the transverse
momenta of the jets. Existing Tevatron data and forthcoming LHC data can
constrain (or discover!) maverick dark matter.Comment: 11 pages, 7 figure
Heavy Quark Spectroscopy -- Theory Overview
Some recent discoveries in the spectroscopy of hadrons containing heavy
quarks, and some of their theoretical interpretations, are reviewed.Comment: 13 pages, 6 figures. Presented at Second Meeting of APS Topical Group
on Hadron Physics, Nashville, TN, 22-24. Proceedings to be published by
Journal of Physics (UK), Conference Series. Uses jpconf.cls, jpconf11.clo.
Some corrections; references update
Maximum Significance at the LHC and Higgs Decays to Muons
We present a new way to define and compute the maximum significance
achievable for signal and background processes at the LHC, using all available
phase space information. As an example, we show that a light Higgs boson
produced in weak--boson fusion with a subsequent decay into muons can be
extracted from the backgrounds. The method, aimed at phenomenological studies,
can be incorporated in parton--level event generators and accommodate
parametric descriptions of detector effects for selected observables.Comment: 7 pages, 2 figures, changes to wording and new references, published
versio
QCD sum rules analysis of the rare B_c \rar X\nu\bar{\nu} decays
Taking into account the gluon correction contributions to the correlation
function, the form factors relevant to the rare B_c \rar X \nu\bar{\nu}
decays are calculated in the framework of the three point QCD sum rules, where
stands for axial vector particle, , and vector particles,
. The total decay width as well as the branching ratio of these
decays are evaluated using the dependent expressions of the form factors.
A comparison of our results with the predictions of the relativistic
constituent quark model is presented.Comment: 21 Pages, 2 Figures and 5 Table
Improving the sensitivity of Higgs boson searches in the golden channel
Leptonic decays of the Higgs boson in the ZZ* channel yield what is known as
the golden channel due to its clean signature and good total invariant mass
resolution. In addition, the full kinematic distribution of the decay products
can be reconstructed, which, nonetheless, is not taken into account in
traditional search strategy relying only on measurements of the total invariant
mass. In this work we implement a type of multivariate analysis known as the
matrix element method, which exploits differences in the full production and
decay matrix elements between the Higgs boson and the dominant irreducible
background from q bar{q} -> ZZ*. Analytic expressions of the differential
distributions for both the signal and the background are also presented. We
perform a study for the Large Hadron Collider at sqrt{s}=7 TeV for Higgs masses
between 175 and 350 GeV. We find that, with an integrated luminosity of 2.5
fb^-1 or higher, improvements in the order of 10 - 20 % could be obtained for
both discovery significance and exclusion limits in the high mass region, where
the differences in the angular correlations between signal and background are
most pronounced.Comment: 31 pages, 8 figures. v2: Minus signs in definitions of angles
corrected. Typos fixed. Reference added. Cosmetic changes to Figure 4.
Additional sentence added for clarificatio
Large CP Violation in B_s Meson Mixing with EDM constraint in Supersymmetry
Motivated by the recent measurement of the like-sign dimuon charge asymmetry,
we investigate anomalous CP violation in the B_s- bar{B}_s mixing within the
supersymmetry. We show that when gluino diagrams dominate supersymmetry
contributions, it is very difficult to realize a large B_s- bar{B}_s mixing
phase under the constraint from electric dipole moments barring cancellations.
This constraint can be ameliorated by supposing superparticles decoupled. In
this limit, we find that it is possible to achieve the large CP asymmetry, and
the branching ratio of B_s -> mu^+ mu^- tends to become sizable.Comment: 20 pages, 5 figure
The Decays to -wave Charmonium by Improved Bethe-Salpeter Approach
We re-calculate the exclusive semileptonic and nonleptonic decays of
meson to a -wave charmonium in terms of the improved Bethe-Salpeter (B-S)
approach, which is developed recently. Here the widths for the exclusive
semileptonic and nonleptonic decays, the form factors, and the charged lepton
spectrums for the semileptonic decays are precisely calculated. To test the
concerned approach by comparing with experimental measurements when the
experimental data are available, and to have comparisons with the other
approaches the results obtained by the approach and those by some approaches
else as well as the original B-S approach, which appeared in literature, are
comparatively presented and discussed.Comment: 33 pages, 5 figures, 3 table
W+W-, WZ and ZZ production in the POWHEG BOX
We present an implementation of the vector boson pair production processes
ZZ, W+W- and W Z within the POWHEG framework, which is a method that allows the
interfacing of NLO calculations to shower Monte Carlo programs. The
implementation is built within the POWHEG BOX package. The Z/\gamma^*
interference, as well as singly resonant contributions, are properly included.
We also considered interference terms arising from identical leptons in the
final state. As a result, all contributions leading to the desired four-lepton
system have been included in the calculation, with the sole exception of the
interference between ZZ and W+W- in the production of a pair of same-flavour,
oppositely charged fermions and a pair of neutrinos, which we show to be fully
negligible. Anomalous trilinear couplings can be also set in the program, and
we give some examples of their effect at the LHC. We have made the relevant
code available at the POWHEG BOX web site.Comment: 20 pages, 9 figures, 2 tables. Minor corrections and updated
references in revised versio
- …