95 research outputs found
Four Light Neutrinos in Singular Seesaw Mechanism with Abelian Flavor Symmetry
The four light neutrino scenario, which explains the atmosphere, solar and
LSND neutrino experiments, is studied in the framework of the seesaw mechanism.
By taking both the Dirac and Majorana mass matrix of neutrinos to be singular,
the four neutrino mass spectrum consisting of two almost degenerate pairs
separated by a mass gap eV is naturally generated. Moreover the
right-handed neutrino Majorana mass can be at GeV scale unlike
in the usual singular seesaw mechanism. Abelian flavor symmetry is used to
produce the required neutrino mass pattern. A specific example of the flavor
charge assignment is provided to show that maximal mixings between the
and are respectively attributed to the
atmosphere and solar neutrino anomalies while small mixing between two pairs to
the LSND results. The implication in the other fermion masses is also
discussed.Comment: Firnal version to appear in PR
Spectral functions of the Falicov-Kimball model with electronic ferroelectricity
We calculate the angular resolved photoemission spectrum of the
Falicov-Kimball model with electronic ferroelectricity where - and
-electrons have different hoppings. In mix-valence regimes, the presence of
strong scattering processes between - excitons and a hole, created by
emission of an electron, leads to the formation of pseudospin polarons and
novel electronic structures with bandwidth scaling with that of -
excitons. Especially, in the two-dimensional case, we find that flat regions
exist near the bottom of the quasiparticle band in a wide range of the - and
-level energy difference.Comment: 5 pages, 5 figure
Lepton Flavor Violating Z Decays in the Zee Model
We calculate lepton flavor violating (LFV) Z decays Z \to {{e_i^\pm}}e_j^\mp
(i, j = e, \mu, \tau ; i\neq j) in the Zee model keeping in view the radiative
leptonic decays e_i\to e_j\gamma (i = \mu, \tau ; j = e, \mu ; i\neq j), \mu
decay and anomalous muon magnetic moment (\mu AMM). We investigate three
different cases of Zee f_{ij} coupling (A) f_{e\mu}^2 = f_{\mu\tau}^2= f_{\tau
e}^2, (B) f_{e\mu}^2 \gg f_{\tau e}^2 \gg f_{\mu\tau}^2, and (C) f_{\mu\tau}^2
\gg f_{e\mu}^2 \gg f_{\tau e}^2 subject to the neutrino phenomenology.
Interestingly, we find that, although the case (C) satisfies the large excess
value of \mu AMM, however, it is unable to explain the solar neutrino
experimental result, whereas the case (B) satisfies the bi-maximal neutrino
mixing scenario, but confronts with the result of \mu AMM experiment. We also
find that among all the three cases, only the case (C) gives rise to largest
contribution to the ratio B(Z\to e^\pm\tau^\mp)/B(Z\to \mu^\pm \mu^\mp) \simeq
{10}^{-8} which is still two order less than the accessible value to be probed
by the future linear colliders, whereas for the other two cases, this ratio is
too low to be observed even in the near future for all possible LFV Z decay
modes.Comment: 12 pages, RevTex, 2 figures, 3 Tables, typos corrected, reference
added, version to appear in Phys. Rev.
Patterns of first-line targeted therapy utilization and adherence among older adults diagnosed with metastatic renal cell carcinoma
Background: Despite the rapid approval of targeted therapies for metastatic renal cell carcinoma (mRCC) evidence on real world treatment patterns remains limited. This study evaluated patterns of first-line targeted therapy utilization and adherence in older adults, a population with a high burden of RCC. Methods: 2093 patients aged ≥66 years with a primary diagnosis of mRCC were identified from United States (US)-based cancer registry and administrative claims data (2007–2015). We included only patients with de novo disease. We assessed the initiation of first-line targeted therapy within four months of diagnosis and persistence and adherence to targeted therapy, using the proportion of days covered (PDC). Multivariable logistic regression yielded adjusted odds ratios (ORs) and 95% confidence intervals (CIs) to describe characteristics associated with targeted therapy versus no targeted therapy initiation and for high (≥80% PDC) versus low adherence. Results: 28.8% of patients received first-line targeted therapy within four months of diagnosis, with the proportion of patients receiving targeted therapy increasing over time. Older age (one-year increment OR:0.95 95%CI 0.93, 0.97), high comorbidity burden (OR:0.65 95%CI0.46, 0.93) and clear cell histology (OR:1.54 95%CI 1.19, 2.00) were associated with targeted therapy initiation. 48.2% of patients exhibited a high PDC to oral targeted therapy at 120 days, which was attenuated with inclusion of patients who died during the time period (34.2% PDC ≥80%). Conclusion: Increasing age, high comorbidity burden and non-clear cell histology were associated with decreased targeted therapy initiation among patients with de novo mRCC. Our findings suggest adherence to oral therapies was low; future research exploring the mechanisms and impact of low adherence in this older patient population is warranted
Minimal Mixing of Quarks and Leptons in the SU(3) Theory of Flavour
We argue that flavour mixing, both in the quark and lepton sector, follows
the minimal mixing pattern, according to which the whole of this mixing is
basically determined by the physical mass generation for the first family of
fermions. So, in the chiral symmetry limit when the masses of the lightest (
and ) quarks vanish, all the quark mixing angles vanish. This minimal
pattern is shown to fit extremely well the already established CKM matrix
elements and to give fairly distinctive predictions for the as yet poorly known
ones. Remarkably, together with generically small quark mixing, it also leads
to large neutrino mixing, provided that neutrino masses appear through the
ordinary ``see-saw'' mechanism. It is natural to think that this minimal
flavour mixing pattern presupposes some underlying family symmetry, treating
families of quarks and leptons in a special way. Indeed, we have found a local
chiral family symmetry model which leads, through its dominant
symmetry breaking vacuum configuration, to a natural realization of the
proposed minimal mechanism. It can also naturally generate the quark and lepton
mass hierarchies. Furthermore spontaneous CP violation is possible, leading to
a maximal CP violating phase , in the framework of the
MSSM extended by a high-scale chiral family symmetry.Comment: 52 pages, LaTex, no figures; some typos corrected; journal versio
Neutrino masses in R-parity violating supersymmetric models
We study neutrino masses and mixing in R-parity violating supersymmetric
models with generic soft supersymmetry breaking terms. Neutrinos acquire masses
from various sources: Tree level neutrino--neutralino mixing and loop effects
proportional to bilinear and/or trilinear R-parity violating parameters. Each
of these contributions is controlled by different parameters and have different
suppression or enhancement factors which we identified. Within an Abelian
horizontal symmetry framework these factors are related and specific
predictions can be made. We found that the main contributions to the neutrino
masses are from the tree level and the bilinear loops and that the observed
neutrino data can be accommodated once mild fine-tuning is allowed.Comment: 18 pages; minor typos corrected. To be published in Physical Review
Restoration of factorization for low hadron hadroproduction
We discuss the applicability of the factorization theorem to low-
hadron production in hadron-hadron collision in a simple toy model, which
involves only scalar particles and gluons. It has been shown that the
factorization for high- hadron hadroproduction is broken by soft gluons in
the Glauber region, which are exchanged among a transverse-momentum-dependent
(TMD) parton density and other subprocesses of the collision. We explain that
the contour of a loop momentum can be deformed away from the Glauber region at
low , so the above residual infrared divergence is factorized by means of
the standard eikonal approximation. The factorization is then restored in
the sense that a TMD parton density maintains its universality. Because the
resultant Glauber factor is independent of hadron flavors, experimental
constraints on its behavior are possible. The factorization can also be
restored for the transverse single-spin asymmetry in hadron-hadron collision at
low in a similar way, with the residual infrared divergence being
factorized into the same Glauber factor.Comment: 12 pages, 2 figures, version to appear in EPJ
Phenomenology of flavor-mediated supersymmetry breaking
The phenomenology of a new economical SUSY model that utilizes dynamical SUSY
breaking and gauge-mediation (GM) for the generation of the sparticle spectrum
and the hierarchy of fermion masses is discussed. Similarities between the
communication of SUSY breaking through a messenger sector, and the generation
of flavor using the Froggatt-Nielsen (FN) mechanism are exploited, leading to
the identification of vector-like messenger fields with FN fields, and the
messenger U(1) as a flavor symmetry. An immediate consequence is that the first
and second generation scalars acquire flavor-dependent masses, but do not
violate FCNC bounds since their mass scale, consistent with effective SUSY, is
of order 10 TeV. We define and advocate a minimal flavor-mediated model (MFMM),
recently introduced in the literature, that successfully accommodates the small
flavor-breaking parameters of the standard model using order one couplings and
ratios of flavon field vevs. The mediation of SUSY breaking occurs via two-loop
log-enhanced GM contributions, as well as several one-loop and two-loop
Yukawa-mediated contributions for which we provide analytical expressions. The
MFMM is parameterized by a small set of masses and couplings, with values
restricted by several model constraints and experimental data. The
next-to-lightest sparticle (NLSP) always has a decay length that is larger than
the scale of a detector, and is either the lightest stau or the lightest
neutralino. Similar to ordinary GM models, the best collider search strategies
are, respectively, inclusive production of at least one highly ionizing track,
or events with many taus plus missing energy. In addition, D^0 - \bar{D}^0
mixing is also a generic low energy signal. Finally, the dynamical generation
of the neutrino masses is briefly discussed.Comment: 54 pages, LaTeX, 8 figure
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