36,691 research outputs found
A Lattice Test of 1/N_c Baryon Mass Relations
1/N_c baryon mass relations are compared with lattice simulations of baryon
masses using different values of the light-quark masses, and hence different
values of SU(3) flavor-symmetry breaking. The lattice data clearly display both
the 1/N_c and SU(3) flavor-symmetry breaking hierarchies. The validity of 1/N_c
baryon mass relations derived without assuming approximate SU(3)
flavor-symmetry also can be tested by lattice data at very large values of the
strange quark mass. The 1/N_c expansion constrains the form of discretization
effects; these are suppressed by powers of 1/N_c by taking suitable
combinations of masses. This 1/N_c scaling is explicitly demonstrated in the
present work.Comment: 13 pages, 20 figures; v2 version to be published in PR
Neutrinoless double beta decay in effective field theory: the light Majorana neutrino exchange mechanism
We present the first chiral effective theory derivation of the neutrinoless
double beta-decay potential induced by light Majorana
neutrino exchange. The effective-field-theory framework has allowed us to
identify and parameterize short- and long-range contributions previously missed
in the literature. These contributions can not be absorbed into
parameterizations of the single nucleon form factors. Starting from the quark
and gluon level, we perform the matching onto chiral effective field theory and
subsequently onto the nuclear potential. To derive the nuclear potential
mediating neutrinoless double beta-decay, the hard, soft and potential neutrino
modes must be integrated out. This is performed through next-to-next-to-leading
order in the chiral power counting, in both the Weinberg and pionless schemes.
At next-to-next-to-leading order, the amplitude receives additional
contributions from the exchange of ultrasoft neutrinos, which can be expressed
in terms of nuclear matrix elements of the weak current and excitation energies
of the intermediate nucleus. These quantities also control the two-neutrino
double beta-decay amplitude. Finally, we outline strategies to determine the
low-energy constants that appear in the potentials, by relating them to
electromagnetic couplings and/or by matching to lattice QCD calculations.Comment: 20 pages, 6 figure
A 125.5 GeV Higgs Boson in F-SU(5): Imminently Observable Proton Decay, A 130 GeV Gamma-ray Line, and SUSY Multijets & Light Stops at the LHC8
We establish that the light Higgs boson mass in the context of the No-Scale
Flipped SU(5) GUT with TeV scale vector-like matter multiplets (flippons) is
consistent with m_h = 125.5+-0.5 GeV in the region of the best supersymmetry
(SUSY) spectrum fit to low statistics data excesses observed by ATLAS in
multijet and light stop 5/fb SUSY searches at the LHC7. Simultaneous
satisfaction of these disparate goals is achieved by employing a minor decrease
in the SU(5) partial unification scale M_{32} to lower the flippon mass,
inducing a larger Higgs boson mass shift from the flippon loops. The reduction
in M_{32}, which is facilitated by a phenomenologically favorable reduction of
the low-energy strong coupling constant, moreover suggests an imminently
observable (e|mu)^+ pi^0 proton decay with a central value time scale of
1.7x10^34 years. At the same point in the model space, we find a lightest
neutralino mass of m_{\chi} = 145 GeV, which is suitable for the production of
130 GeV monochromatic gamma-rays through annihilations yielding associated
Z-bosons; a signal with this energy signature has been identified within
observations of the galactic center by the FERMI-LAT Space Telescope. In
conjunction with direct correlations to the fate of the ATLAS multijet and
light stop production channels presently being tested at the LHC8, we suggest
that the reality of a 125.5 GeV Higgs boson affords a particularly rich company
of specific and imminently testable associated observables.Comment: European Physical Journal C Version; 10 Pages, 2 Figures, 2 Table
Profumo di SUSY: Suggestive Correlations in the ATLAS and CMS High Jet Multiplicity Data
We present persistently amassing evidence that the CMS and ATLAS
Collaborations may indeed be already registering supersymmetry events at the
Large Hadron Collider (LHC). Our analysis is performed in the context of a
highly phenomenologically favorable model named No-Scale F-SU(5), which
represents the unification of the F-lipped SU(5) Grand Unified Theory (GUT),
two pairs of hypothetical TeV-scale vector-like supersymmetric multiplets
derived out of F-Theory, and the dynamically established boundary conditions of
No-Scale supergravity. We document highly suggestive correlations between the
first inverse femtobarn of observations by CMS and ATLAS, where seductive
excesses in multijet events, particularly those with nine or more jets, are
unambiguously accounted for by a precision Monte-Carlo simulation of the
F-SU(5) model space. This intimate correspondence is optimized by a unified
gaugino mass in the neighborhood of M_{1/2}=518 GeV. We supplement this
analysis by extrapolating for the expected data profile to be realized with
five inverse femtobarns of integrated luminosity, as expected to be observed at
the LHC by the conclusion of 2011. Significantly, we find that this luminosity
may be sufficient to constitute a SUSY discovery for the favored benchmark
spectrum. Indeed, the winds wafting our way from Geneva may already be heavy
with the delicate perfume of Supersymmetry.Comment: 15 pages, 5 figures, 6 table
Non-trivial Supersymmetry Correlations between ATLAS and CMS Observations
We present definite correlations between the CMS 5 \fb all-hadronic search
employing the stransverse mass variable and the ATLAS 5 \fb
all-hadronic and multijet supersymmetry (SUSY) searches, suggesting the
possibility that both the ATLAS and CMS experiments are already registering a
faint but legitimate SUSY signal at the LHC. We isolate this prospective mutual
productivity beyond the Standard Model in the framework of the supersymmetric
No-Scale Flipped (5) grand unified theory, supplemented with extra
vector-like matter (flippons). Evident overproduction is observed in three CMS
\mt2 and four ATLAS hadronic and multijet signal regions, where a \x2 fitting
procedure of the CMS 5 \fb \mt2 search establishes a best fit SUSY mass in
sharp agreement with corresponding ATLAS searches of equivalently heightened
signal significance. We believe this correlated behavior across two distinct
experiments at precisely the same SUSY mass scale to be highly non-trivial, and
potentially indicative of an existing 5 \fb LHC reach into a pervasive physical
supersymmetry framework.Comment: 6 Pages, 2 Figure
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