1,316 research outputs found
Decoupling heavy sparticles in Effective SUSY scenarios: Unification, Higgs masses and tachyon bounds
Using two-loop renormalization group equations implementing the decoupling of
heavy scalars, Effective SUSY scenarios are studied in the limit in which there
is a single low energy Higgs field. Gauge coupling unification is shown to hold
with similar or better precision than in standard MSSM scenarios. b-tau
unification is examined, and Higgs masses are computed using the effective
potential, including two-loop contributions from scalars. A 125 GeV Higgs is
compatible with stops/sbottoms at around 300 GeV with non-universal boundary
conditions at the scale of the heavy sparticles if some of the trilinear
couplings at this scale take values of the order of 1-2 TeV; if more
constrained boundary conditions inspired by msugra or gauge mediation are set
at a higher scale, heavier colored sparticles are required in general. Finally,
since the decoupled RG flow for third-generation scalar masses departs very
significantly from the MSSM DR-bar one, tachyon bounds for light scalars are
revisited and shown to be relaxed by up to a TeV or more.Comment: 35 pages, 17 figures. v2: Updated some scans, allowing for changes in
sign of some parameters, minor improvements. v3: Typos corrected in formulae
in the appendices, added some clarifying remarks about flavor mixing being
ignore
Superpartner spectrum of minimal gaugino-gauge mediation
We evaluate the sparticle mass spectrum in the minimal four-dimensional
construction that interpolates between gaugino and ordinary gauge mediation at
the weak scale. We find that even in the hybrid case -- when the messenger
scale is comparable to the mass of the additional gauge particles -- both the
right-handed as well as the left-handed sleptons are lighter than the bino in
the low-scale mediation regime. This implies a chain of lepton production and,
consequently, striking signatures that may be probed at the LHC already in the
near future.Comment: 8 pages, 3 figures; V2: refs and a few comments added; V3 title
change
Changes to healthcare utilisation and symptoms for common mental health problems over the first 21 months of the COVID-19 pandemic: parallel analyses of electronic health records and survey data in England
BACKGROUND:
Few studies have investigated the effect of the COVID-19 pandemic on mental health beyond 2020. This study quantifies changes to healthcare utilisation and symptoms for common mental health problems over the pandemic’s first 21 months.
METHODS:
Parallel cohort studies using primary care database and survey data for adults (≥16 years) in England from January 2015 to December 2021: 16,551,842 from the Clinical Practice Research Datalink (CPRD) and 40,699 from the UK Household Longitudinal Survey (UKHLS). Interrupted time-series models estimated changes in monthly prevalence of presentations and prescribed medications for anxiety and depression (CPRD); and self-reported psychological distress (UKHLS). The pandemic period was divided into five phases: 1st Wave (April–May 2020); post-1st Wave (June–September 2020); 2nd Wave (October 2020–February 2021); post 2nd Wave (March–May 2021); 3rd Wave (June–December 2021).
FINDINGS:
Primary care presentations for depression or anxiety dropped during the first wave (4.6 fewer monthly appointments per 1000 patients, 4.4–4.8) and remained lower than expected throughout follow-up. Self-reported psychological distress exceeded expected levels during the first (Prevalence Ratio = 1.378, 95% CI 1.289–1.459) and second waves (PR = 1.285, 1.189–1.377), returning towards expected levels during the third wave (PR = 1.038, 0.929–1.154). Increases in psychological distress and declines in presentations were greater for women. The decrease in primary care presentations for depression and anxiety exceeded that for physical health conditions (rheumatoid arthritis, diabetes, urinary tract infections). Anxiety and depression prescriptions returned to pre-pandemic levels during the second wave due to increased repeat prescriptions.
INTERPRETATION:
Despite periods of distress during the pandemic, we did not find an enduring effect on common mental health problems. The fall in primary care presentations for anxiety or depression suggests changing healthcare utilisation for mental distress and a potential treatment gap.
FUNDING:
National Institute for Health and Care Research (NIHR)
Yukawa unification in SO(10) with light sparticle spectrum
We investigate supersymmetric SO(10) GUT model with \mu<0. The requirements
of top-bottom-tau Yukawa unification, correct radiative electroweak symmetry
breaking and agreement with the present experimental data may be met when the
soft masses of scalars and gauginos are non-universal. We show how appropriate
non-universalities can easily be obtained in the SO(10) GUT broken to the
Standard Model. We discuss how values of BR(b-->s \gamma) and (g-2)_\mu
simultaneously in a good agreement with the experimental data can be achieved
in SO(10) model with \mu<0. In the region of the parameter space preferred by
our analysis there are two main mechanisms leading to the LSP relic abundance
consistent with the WMAP results. One is the co-annihilation with the stau and
the second is the resonant annihilation via exchange of the Z boson or the
light Higgs scalar. A very interesting feature of SO(10) models with negative
\mu is that they predict relatively light sparticle spectra. Even the heaviest
superpartners may easily have masses below 1.5 TeV in contrast to multi-TeV
particles typical for models with positive \mu.Comment: 23 pages, 5 figure
LHC Discovery Potential for Non-Standard Higgs Bosons in the 3b Channel
In a variety of well motivated models, such as two Higgs Doublet Models
(2HDMs) and the Minimal Supersymmetric Standard Model (MSSM), there are neutral
Higgs bosons that have significantly enhanced couplings to b-quarks and tau
leptons in comparison to those of the SM Higgs. These so called non-standard
Higgs bosons could be copiously produced at the LHC in association with b
quarks, and subsequently decay into b-quark pairs. However, this production
channel suffers from large irreducible QCD backgrounds. We propose a new search
strategy for non-standard neutral Higgs bosons at the 7 TeV LHC in the 3b's
final state topology. We perform a simulation of the signal and backgrounds,
using state of the art tools and methods for different sets of selection cuts,
and conclude that neutral Higgs bosons with couplings to b-quarks of about 0.3
or larger, and masses up to 400 GeV, could be seen with a luminosity of 30
fb^{-1}. In the case of the MSSM we also discuss the complementarity between
the 3b channel and the inclusive tau pair channel in exploring the
supersymmetric parameter space.Comment: 14 pages, 3 figures, 4 tables, references added, published versio
A 125 GeV SM-like Higgs in the MSSM and the rate
We consider the possibility of a Standard Model (SM)-like Higgs in the
context of the Minimal Supersymmetric Standard Model (MSSM), with a mass of
about 125 GeV and with a production times decay rate into two photons which is
similar or somewhat larger than the SM one. The relatively large value of the
SM-like Higgs mass demands stops in the several hundred GeV mass range with
somewhat large mixing, or a large hierarchy between the two stop masses in the
case that one of the two stops is light. We find that, in general, if the
heaviest stop mass is smaller than a few TeV, the rate of gluon fusion
production of Higgs bosons decaying into two photons tends to be somewhat
suppressed with respect to the SM one in this region of parameters. However, we
show that an enhancement of the photon decay rate may be obtained for light
third generation sleptons with large mixing, which can be naturally obtained
for large values of and sizable values of the Higgsino mass
parameter.Comment: 14 pages, 4 figures. Corrected small typos and added reference
Higgs and Dark Matter Hints of an Oasis in the Desert
Recent LHC results suggest a standard model (SM)-like Higgs boson in the
vicinity of 125 GeV with no clear indications yet of physics beyond the SM. At
the same time, the SM is incomplete, since additional dynamics are required to
accommodate cosmological dark matter (DM). In this paper we show that
interactions between weak scale DM and the Higgs which are strong enough to
yield a thermal relic abundance consistent with observation can easily
destabilize the electroweak vacuum or drive the theory into a non-perturbative
regime at a low scale. As a consequence, new physics--beyond the DM
itself--must enter at a cutoff well below the Planck scale and in some cases as
low as O(10 - 1000 TeV), a range relevant to indirect probes of flavor and CP
violation. In addition, this cutoff is correlated with the DM mass and
scattering cross-section in a parameter space which will be probed
experimentally in the near term. Specifically, we consider the SM plus
additional spin 0 or 1/2 states with singlet, triplet, or doublet electroweak
quantum numbers and quartic or Yukawa couplings to the Higgs boson. We derive
explicit expressions for the full two-loop RGEs and one-loop threshold
corrections for these theories.Comment: 29 pages, 13 figure
Fair scans of the seesaw. Consequences for predictions on LFV processes
Usual analyses based on scans of the seesaw parameter-space can be biassed
since they do not cover in a fair way the complete parameter-space. More
precisely, we show that in the common "R-parametrization", many acceptable
R-matrices, compatible with the perturbativity of Yukawa couplings, are
normally disregarded from the beginning, which produces biasses in the results.
We give a straightforward procedure to scan the space of complex R-matrices in
a complete way, giving a very simple rule to incorporate the perturbativity
requirement as a condition for the entries of the R-matrix, something not
considered before. As a relevant application of this, we show that the extended
believe that BR(mu --> e, gamma) in supersymmetric seesaw models depends
strongly on the value of theta_13 is an "optical effect" produced by such
biassed scans, and does not hold after a careful analytical and numerical
study. When the complete scan is done, BR(mu --> e, gamma) gets very
insensitive to theta_13. Moreover, the values of the branching ratio are
typically larger than those quoted in the literature, due to the large number
of acceptable points in the parameter-space which were not considered before.
Including (unflavoured) leptogenesis does not introduce any further dependence
on theta_13, although decreases the typical value of BR(mu --> e, gamma).Comment: 22 pages, 5 figure
Hadronic production of bottom-squark pairs with electroweak contributions
We present the complete computation of the tree-level and the next-to-leading
order electroweak contributions to bottom-squark pair production at the LHC.
The computation is performed within the minimal supersymmetric extension of the
Standard Model. We discuss the numerical impact of these contributions in
several supersymmetric scenarios.Comment: 33 pages, v2: preprint numbers correcte
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