4,802 research outputs found
Matter parity as the origin of scalar Dark Matter
We extend the concept of matter parity to
non-supersymmetric theories and argue that is the natural explanation to
the existence of Dark Matter of the Universe. We show that the
non-supersymmetric Dark Matter must be contained in scalar 16 representation(s)
of thus the unique low energy Dark Matter candidates are -odd
complex scalar singlet(s) and inert scalar doublet(s) We have
calculated the thermal relic Dark Matter abundance of the model and shown that
its minimal form may be testable at LHC via the SM Higgs boson decays The PAMELA anomaly can be explained with the decays
induced via seesaw-like operator which is additionally suppressed by Planck
scale. Because the SM fermions are odd under matter parity too, the DM sector
is just our scalar relative.Comment: The origin of scalar DM is emphasized, version accepted by PR
A Natural Framework for Bi-large Neutrino Mixing
In this letter we present a "natural" framework for obtaining bi-large
neutrino mixing incorporating the FGY neutrino mass matrix ansatz. We show that
an family symmetry can provide the desired FGY neutrino
mass ansatz in the MSSM. We also show how to obtain an approximate FGY ansatz
in an SO(10) SUSY GUT. In this context, the same family
symmetry also generates the hierarchy of fermion masses as well as ameliorating
SUSY flavor problems.Comment: 10 pages, no figures, extended discussion of standard model version
including charged lepton analysi
Single Production of Doubly Charged Higgsinos at linear e-e- colliders
Several extended supersymmetric models, motivated by either grand
unification, or by neutrino mass generation, predict light doubly charged
higgsinos. We study the production of a single doubly charged higgsino and its
decay channels at the International Linear Collider (ILC) operating in the e-e-
mode. We analyze the production cross section for e-e- -->
tilde{Delta}^{--}_{L,R} chi^0_1 as a function of different kinematic variables,
followed by the decay, through several channels, of the doubly charged higgsino
into a final state of two leptons plus missing energy. We include the standard
model background and discuss how kinematic cuts could be used effectively to
limit this background. Single production of these exotics could provide a
spectacular signal for a new underlying symmetry and for physics beyond the
minimal supersymmetric standard model.Comment: Typos corrected, Journal Versio
Single Top Production at the Next Generation Linear e+e- Colliders
Present limits on the top mass from LEP1 and Tevatron point to a top quark
that is considerably heavier than the vector boson in the standard model.
Hence, e+e- colliders with \sqrt{s} \simeq 300 GeV (the c.m. energy foreseen at
the first phase of the Next Linear e+e- Collider) could be well below the
energy threshold for real top-pair production. We argue that, if this is the
case, single top production through the process e+e- --> t\bar{b}W-
(\bar{t}bW+), where t\bar{b} (\bar{t}b) are produced mainly by means of a
virtual W, becomes the dominant top production mechanism. Total cross sections
and kinematical distributions are evaluated and numerical results are given in
ranges of m_t and \sqrts{s} where single top production can be of relevance.
The relative importance of virtual-W and virtual-t contributions to the process
is discussed.Comment: 20 pages, LaTeX + feynman.tex, 10 compressed (tar.Z) postscript
figures included in a separate uuencoded file, revised version of Rome1
Preprint n.979 (1993), Dec 29, 1993. (In this revised version -- accepted for
publication on Zeit. fur Phys.C in Jan 24, 1994 -- some sentences and 3 new
refs. have been added with respect to the first one
Relation between the neutrino and quark mixing angles and grand unification
We argue that there exists simple relation between the quark and lepton
mixings which supports the idea of grand unification and probes the underlying
robust bi-maximal fermion mixing structure of still unknown flavor physics. In
this framework the quark mixing matrix is a parameter matrix describing the
deviation of neutrino mixing from exactly bi-maximal, predicting
theta_{sol}+theta_C=pi/4, where theta_C is the Cabibbo angle,
theta_{atm}+theta_{23}^{CKM}=pi/4 and theta_{13}^{MNS} ~ theta_{13}^{CKM} ~
O(lambda^3), in a perfect agreement with experimental data. Both non-Abelian
and Abelian flavor symmetries are needed for such a prediction to be realistic.
An example flavor model capable to explain this flavor mixing pattern, and to
induce the measured quark and lepton masses, is outlined.Comment: references added, title changed in journa
Dark Matter as the signal of Grand Unification
We argue that the existence of Dark Matter (DM) is a possible consequence of
GUT symmetry breaking. In GUTs like SO(10), discrete Z_2 matter parity
(-1)^{3(B-L)} survives despite of broken B-L, and group theory uniquely
determines that the only possible Z_2-odd matter multiplets belong to
representation 16. We construct the minimal non-SUSY SO(10) model containing
one scalar 16 for DM and study its predictions below M_{G}. We find that EWSB
occurs radiatively due to DM couplings to the SM Higgs boson. For thermal relic
DM the mass range M_{DM}\sim (0.1-1) TeV is predicted by model perturbativity
up to M_{G}. For M_{DM}\sim (1) TeV to explain the observed cosmic ray
anomalies with DM decays, there exists a lower bound on the spin-independent
direct detection cross section within the reach of planned experiments.Comment: DM direct detection cross section is corrected by adding s-quark
contribution which turned out to be the dominant one. The prediction is just
below the present CDMS and XENON10 bound. Extended version, RGE-s included,
new references adde
CP Violation in the Minimal Supersymmetric Seesaw Model
We study CP violation in the lepton sector of the supersymmetric extension of the Standard Model with three generations of massive singlet neutrinos with Yukawa couplings to lepton doublets, in a minimal seesaw model for light neutrino masses and mixing. This model contains six physical CP-violating parameters, namely the phase observable in oscillations between light neutrino species, two Majorana phases that affect decays, and three independent phases appearing in , that control the rate of leptogenesis. Renormalization of the soft supersymmetry-breaking parameters induces observable CP violation at low energies, including T-odd asymmetries in polarized and decays, as well as lepton electric dipole moments. In the leading-logarithmic approximation in which the massive singlet neutrinos are treated as degenerate, these low-energy observables are sensitive via to just one combination of the leptogenesis and light-neutrino phases. We present numerical results for the T-odd asymmetry in polarized decay, which may be accessible to experiment, but the lepton electric dipole moments are very small in this approximation. To the extent that the massive singlet neutrinos are not degenerate, low-energy observables become sensitive also to two other combinations of leptogenesis and light-neutrino phases, in this minimal supersymmetric seesaw model
Enhancement of Radiatively Induced Magnetic Moment Form-Factors of Muon: an Effective Lagrangian Approach
Using an effective lagrangian approach, we identify a class of models in
which the loop-induced magnetic moment form-factors of muon are enhanced by
possibly large factors
(\Lambda^2_F/\Lambda^2)(m_\tau/m_\mu)\ln(m_\tau^2/\Lambda^2) or
(\Lambda^2_F/\Lambda^2)\ln(m_\mu^2/\Lambda^2), where \Lambda is the scale of
new physics and \Lambda_F is the Fermi scale. These follow from left- and
right-chirality mixing dimension-8 operators which for relatively small
\Lambda, as required to explain the new (g_\mu-2) measurement, dominate over
dimension-6 operators. Thus significant enhancement of new physics
contributions to (g_\mu-2) and, in the presence of intergenerational couplings,
also to the \mu\to e\gamma decay rate is possible. We discuss the compatibility
of the (g_\mu-2) and \mu\to e\gamma experimental data in this case and comment
on the enhancement of the electron anomalous magnetic moment. An explicit model
is presented to illustrate the general results.Comment: Discussion on the enhancement of electron anomalous magnetic moment
included. New references adde
Effects of Transport and Feeding Strategies Before Transportation on Redox Homeostasis and Gastric Ulceration in Horses
Transportation may lead to oxidative stress (OS) and gastric ulceration in horses, and optimal feed man-agement before, or during, transportation is unclear. This study aimed to evaluate the effects of trans-portation after three different feeding strategies on OS and to explore possible associations between OS and equine gastric ulcer syndrome (EGUS). Twenty-six mares were transported by truck for 12 hours without food or water. Horses were randomly divided into 3 groups; (1) fed 1 hour before departure (BD), (2) fed 6 hours BD, (3) fed 12 hours BD. Clinical examinations and blood collections were per-formed at approximately 4 hours BD (T0), at unloading (T1), 8 hours (T2) and 60 hours (T3) after un-loading. Gastroscopy was conducted prior to departure, and at T1 and T3. Although OS parameters re-mained in the normal range, transportation was associated with increased reactive oxygen metabolites (ROMS) at unloading (P = 0.004), with differences between horses fed 1 hour and 12 hours BD ( P < .05). The level of total antioxidant (PTAS) was affected by both transportation and feeding strategy ( P = 0.019), with horses fed 1 hour BD demonstrating greater PTAS at T = 0, and a different response in comparison with the other groups and the literature. Nine horses demonstrated clinically significant ulceration of the squamous mucosa at T1 but, although weak correlations were evident between OS parameters and ulcer scores, univariate logistic regression showed no associations. This study suggests that feed management prior to a long journey (12 hours) may affect oxidative balance. Further studies are needed to understand the nexus between feed management before and during transport, transport-related OS and EGUS.(c) 2023 Elsevier Inc. All rights reserved
Respiratory Support for Pharmacologically Induced Hypoxia in Neonatal Calves
Practical methods to provide respiratory support to bovine neonates in a field setting are poorly characterised. This study evaluated the response of healthy neonatal calves with pharmacologically induced respiratory suppression to nasal oxygen insufflation and to continuous positive airway pressure (CPAP) delivered via an off-the-shelf device. Ten calves were randomised to receive either nasal oxygen insufflation (Group 1, n=5) or CPAP (Group 2, n=5) as a first treatment after induction of respiratory depression by intravenous administration of xylazine, fentanyl, and diazepam. Calves received the alternate treatment after 10 minutes of breathing ambient air. Arterial blood gas samples were obtained prior to sedation, following sedation, following the first and second treatment, and after breathing ambient air before and after the second treatment. Oxygen insufflation significantly increased arterial oxygen partial pressure (PaO2) but was also associated with significant hypercapnia. When used as the first treatment, CPAP was associated with significantly decreased arterial partial pressure of carbon dioxide but did not increase PaO2. These results suggest that the use of CPAP may represent a practical method for correction of hypercapnia associated with inadequate ventilation in a field setting, and further research is required to characterise the use of CPAP with increased inspired oxygen concentrations
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