146 research outputs found
Lectures on Flavor Physics and CP Violation
Two short introductory lectures on Flavor Physics delivered at CLASHEP 2015.
Among included topics: The KM matrix and the KM model of CP-violation,
Determination of KM Elements, FCNC and GIM, New Physics and Flavor, Neutral
Meson Mixing and CP Asymmetries. Many problems for the student, and solutions
to selected problems, included.Comment: Presented at the 2015 CERN-Latin-American School of High-Energy
Physics, Ibarra, Ecuador, 5 - 17 March 2015. arXiv admin note: substantial
text overlap with arXiv:1501.0528
Weyl Consistency Conditions in Non-Relativistic Quantum Field Theory
Weyl consistency conditions have been used in unitary relativistic quantum
field theory to impose constraints on the renormalization group flow of certain
quantities. We classify the Weyl anomalies and their renormalization scheme
ambiguities for generic non-relativistic theories in 2+1 dimensions with
anisotropic scaling exponent z=2; the extension to other values of z are
discussed as well. We give the consistency conditions among these anomalies. As
an application we find several candidates for a C-theorem. We comment on
possible candidates for a -theorem in higher dimensions.Comment: 38 pages, 1 figure, 7 tables; We took out the section on arbitrary
dimension in version:2 !! In version:3 , a section (Sec: V) with NEW RESULTS
on possible C-theorem candidates in arbitrary dimensions is added; v4:matched
with journal version and updated section I
Carving Out Parameter Space in Type-II Two Higgs Doublets Model
We analyze the Type-II two Higgs doublets model in light of the newly
discovered Higgs-like particle with mass 125 GeV. The observed 125 GeV particle
is identified with the light CP-even Higgs boson in the two Higgs doublets
model. We study the parameter space of the model consistent with the Higgs
data, branching ratio of as well as precision
electroweak measurements. We also incorporate theoretical constraints---
perturbativity of the couplings and vacuum stability, in our study. We find
that only a small parameter space of the model remains viable. The
phenomenology of the heavy Higgs bosons in the surviving parameter space is
studied.Comment: Revise the CP odd scalar branching ratios. Main conclusion remains
unchange
Factorization in B -> K pi e+e- decays
We derive factorization relations for the transverse helicity amplitudes in
the rare decays B-> K\pi l+l- at leading order in Lambda/m_b, in the
kinematical region with an energetic kaon and a soft pion. We identify and
compute a new contribution of leading order in Lambda/m_b to the B->K\pi l+l-
amplitude, which is not present in the one-body decay B-> K*l+l-. As an
application we study the forward-backward asymmetry (FBA) of the lepton
momentum angular distribution in B-> K\pi l+l- decays away from the K*
resonance. The FBA in these decays has a zero at q0^2 = q0^2(M_{Kpi}), which
can be used, in principle, for determining the Wilson coefficients C_{7,9} and
testing the Standard Model. We point out that the slope of the q0^2(M_{Kpi}^2)
curve contains the same information about the Wilson coefficients as the
location of the zero, but is less sensitive to unknown nonperturbative
dynamics. We estimate the location of the zero at leading order in
factorization, and using a resonant model for the B -> K\pi l+l-
nonfactorizable amplitude.Comment: 16 pages, 5 figures. Version to appear in Physical Review D. One new
observable introduced and considered - the slope of the zero of the
forward-backward asymmetry as function of the K\pi invariant mas
Bottom-Quark Forward-Backward Asymmetry in the Standard Model and Beyond
We computed the bottom-quark forward-backward asymmetry at the Tevatron in
the Standard Model and for several new physics scenarios. Near the -pole,
the SM bottom asymmetry is dominated by tree level exchanges of electroweak
gauge bosons. While above the -pole, next-to-leading order QCD dominates the
SM asymmetry as was the case with the top quark forward-backward asymmetry.
Light new physics, GeV, can cause significant deviations
from the SM prediction for the bottom asymmetry. The bottom asymmetry can be
used to distinguish between competing NP explanations of the top asymmetry
based on how the NP interferes with s-channel gluon and exchange.Comment: v3: Bug found in FeynRules 1.6.1 (not present in current version,
2.0.24) One plot corrected. Conclusions unaffecte
Weak decays of unstable -mesons
We investigate the decays of the excited mesons as probes of the
short-distance structure of the weak transitions. These states are
unstable under the electromagnetic or strong interactions although their widths
are typically suppressed by phase space. As compared to the pseudoscalar
meson, the purely leptonic decays of the vector are not chirally
suppressed and are sensitive to different combinations of the underlying weak
effective operators. An interesting example is , which
has a rate that can be accurately predicted in the standard model. The
branching fraction is , irrespective of the lepton
flavor and where the main uncertainty stems from the unmeasured and
theoretically not-well known width. We discuss the prospects for
producing this decay mode at the LHC and explore the possibility of measuring
the amplitude, instead, through scattering experiments at
the resonance peak. Finally we also discuss the charged-current
decay which can provide complementary information on the
and transitions.Comment: 21 page
Ultraviolet Properties of the Higgs Sector in the Lee-Wick Standard Model
The Lee-Wick (LW) Standard Model (SM) offers a new solution to the hierarchy
problem. We discuss, using effective potential techniques, its peculiar
ultraviolet (UV) behaviour. We show how quadratic divergences in the Higgs mass
Mh cancel as a result of the unusual dependence of LW fields on the Higgs
background (in a manner reminiscent of Little Higgses). We then extract from
the effective potential the renormalization group evolution of the Higgs
quartic coupling lambda above the LW scale. After clarifying an apparent
discrepancy with previous results for the LW Abelian Higgs model we focus on
the LWSM. In contrast with the SM case, for any Mh, lambda grows monotonically
and hits a Landau pole at a fixed trans-Planckian scale (never turning negative
in the UV). Then, the perturbativity and stability bounds on Mh disappear. We
identify a cutoff ~10^{16} GeV for the LWSM due to the hypercharge gauge
coupling hitting a Landau pole. Finally, we also discuss briefly the possible
impact of the UV properties of the LW models on their behaviour at finite
temperature, in particular regarding symmetry nonrestoration.Comment: 25 pages, 3 figure
Searching for New Physics in the Three-Body Decays of the Higgs-like Particle
We show that the three-body decays of the resonance recently discovered at
the LHC are potentially sensitive to effects of new physics. Even if the fully
integrated partial decay widths are consistent with the minimal Standard Model
there is information that is lost upon integration, which can be uncovered in
the differential decay widths. Concentrating on the decay , we identify the regions in the three-body phase space in which
these effects become especially pronounced and could be detected in future
experiments.Comment: 20 pages, 5 figures, matches version published in JHE
Theoretical Constraints on Additional Higgs Bosons in Light of the 126 GeV Higgs
We present a sum rule for Higgs fields in general representations under
that follows from the connection between the Higgs
couplings and the mechanism that gives the electroweak bosons their masses, and
at the same time restricts these couplings. Sum rules that follow from
perturbative unitarity will require us to include singly and doubly charged
Higgses in our analysis. We examine the consequences of these sum rules for
Higgs phenomenology in both model independent and model specific ways. The
relation between our sum rules and other works, based on dispersion relations,
is also clarified.Comment: 53 pages, 17 figures. Version 3: expanded references, matched JHEP
versio
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