173 research outputs found
and in Simplified New Physics Models
The decays and , being the
theoretically cleanest rare decays of mesons, are very sensitive probes of New
Physics. In view of the excellent prospects of reaching the Standard Model
sensitivity for by the NA62 experiment at CERN and for
by the KOTO experiment at J-PARC, we study them in the
simplest extensions of the SM in which stringent correlations between these two
decays and other flavour observables are present. We first consider simple
models with tree-level Z and Z' contributions in which either MFV or a
symmetry is imposed on the quark flavour-violating couplings. We then compare
the resulting correlations with those present in generic models in which the
latter couplings are arbitrary, subject to constraints from
processes, electroweak and collider data. Of particular interest are the
correlations with and which limit the
size of NP contributions to and
, depending on the Dirac structure of couplings and the
relevant operators. But in MFV also the constraint from
turns out to be important. We take into account the recent results from lattice
QCD and large N approach that indicate in the SM to be
significantly below the data. While in many models the enhancement of
implies a suppression of , we
present two models in which these observables can be simultaneously enhanced
relative to SM predictions. A correlation between and
, found by us in the simple models considered here,
should be of interest for NA62 and LHCb experimentalists at CERN in the coming
years. The one with will be tested at Belle II.Comment: 32 pages, 6 figures, 1 table. v2: updated analysis in section 4,
matches version published in JHE
Strategies for Fixing the CKM-angle and Obtaining Experimental Insights into the World of Electroweak Penguins
Using the flavour symmetry of strong interactions, we propose
strategies for extracting both the CKM-angle and the tree-level amplitude . We present also an approximate approach
using the branching ratios for the modes , , and which should be rather
promising from the experimental point of view. The quantities and
determined this way may well be used as an input to control electroweak
penguins in nonleptonic -decays as has been discussed in previous work.
Following these lines, we propose strategies for obtaining quantitative
insights into the physics of the electroweak penguin operators and performing
some consistency checks. As a by-product, we derive an upper bound of
for the uncertainty originating from electroweak penguins in the
-determination by means of decays.Comment: 15 pages, LaTeX, Figures not include
Towards the Control over Electroweak Penguins in Nonleptonic B-Decays
We present strategies for determining electroweak penguins from experimental
data. Using the CKM-angle as one of our central inputs and making some
reasonable approximations, we show that the electroweak
penguin amplitude can be determined in a two-step procedure involving i)
BR, BR, BR and ii) either
BR, BR or \acp(t) of the mode
. The determination employing the transitions is not
affected by -breaking effects. Relating the
electroweak penguin amplitude to the case through
symmetry arguments, we are in a position to estimate the electroweak penguin
uncertainty affecting the extraction of the CKM-angle by using isospin
relations among decays. Our results allow in principle the
determination of CKM-phases in a variety of -decays.Comment: 14 pages, LaTeX, Figures not include
Exploring CP Violation through B Decays
The B-meson system provides many strategies to perform stringent tests of the
Standard-Model description of CP violation. In this brief review, we discuss
implications of the currently available B-factory data on the angles alpha,
beta and gamma of the unitarity triangle, emphasize the importance of Bs
studies at hadronic B experiments, and discuss new, theoretically clean
strategies to determine gamma.Comment: 22 pages, 4 figures, invited brief review for Modern Physics Letters
Influence of aerosols, clouds, and sunglint on polarization spectra of Earthshine
Ground-based observations of the Earthshine, i.e., the light scattered by
Earth to the Moon, and then reflected back to Earth, simulate space
observations of our planet and represent a powerful benchmark for the studies
of Earth-like planets. Earthshine spectra are strongly linearly polarized,
owing to scattering by molecules and small particles in the atmosphere of the
Earth and surface reflection, and may allow us to measure global atmospheric
and surface properties of planet Earth. Aims. We aim to interpret already
published spectropolarimetric observations of the Earthshine by comparing them
with new radiative transfer model simulations including a fully realistic
three-dimensional (3D) surface-atmosphere model for planet Earth. We used the
highly advanced Monte Carlo radiative transfer model MYSTIC to simulate
polarized radiative transfer in the atmosphere of the Earth without
approximations regarding the geometry, taking into account the polarization
from surface reflection and multiple scattering by molecules, aerosol
particles, cloud droplets, and ice crystals. We have shown that Earth
spectropolarimetry is highly sensitive to all these input parameters, and we
have presented simulations of a fully realistic Earth atmosphere-surface model
including 3D cloud fields and two-dimensional (2D) surface property maps. Our
modeling results show that scattering in high ice water clouds and reflection
from the ocean surface are crucial to explain the continuum polarization at
longer wavelengths as has been reported in Earthshine observations taken at the
Very Large Telescope in 2011 (3.8 % and 6.6 % at 800 nm, depending on which
part of Earth was visible from the Moon at the time of the observations). We
found that the relatively high degree of polarization of 6.6 % can be
attributed to light reflected by the ocean surface in the sunglint region
B -> pi pi, New Physics in B -> pi K and Implications for Rare K and B Decays
The measured B -> pi pi, pi K branching ratios exhibit puzzling patterns. We
point out that the B -> pi pi hierarchy can be nicely accommodated in the
Standard Model (SM) through non-factorizable hadronic interference effects,
whereas the B -> pi K system may indicate new physics (NP) in the electroweak
(EW) penguin sector. Using the B -> pi pi data and the SU(3) flavour symmetry,
we may fix the hadronic B -> pi K parameters, which allows us to show that any
currently observed feature of the B -> pi K system can be easily explained
through enhanced EW penguins with a large CP-violating NP phase. Restricting
ourselves to a specific scenario, where NP enters only through Z^0 penguins, we
derive links to rare K and B decays, where an enhancement of the K_L-> pi^0 nu
nu_bar rate by one order of magnitude, with BR(K_L -> pi^0 nu nu_bar) > BR(K^+
-> pi^+ nu nu_bar), BR(K_L -> pi^0 e^+ e^-)=O(10^{-10}), (\sin2\beta)_{pi nu
nu_bar} K* mu^+ mu^-,
are the most spectacular effects. We address also other rare K and B decays,
epsilon'/epsilon and B_d -> phi K_S.Comment: 6 pages, LaTeX, reference added and a few typos correced, to appear
in Physical Review Letter
Can we reach the Zeptouniverse with rare K and B_{s,d} decays?
The Large Hadron Collider will directly probe distance scales as short as
10^{-19}m, corresponding to energy scales at the level of a few TeV. In order
to reach even higher resolutions before the advent of future high-energy
colliders, it is necessary to consider indirect probes of New Physics (NP), a
prime example being Delta F=2 neutral meson mixing processes, which are
sensitive to much shorter distance scales. However Delta F=2 processes alone
cannot tell us much about the structure of NP beyond the LHC scales. To
identify for instance the presence of new quark flavour-changing dynamics of a
left-handed (LH) or right-handed (RH) nature, complementary results from Delta
F=1 rare decay processes are vital. We therefore address the important question
of whether NP could be seen up to energy scales as high as 200 TeV,
corresponding to distances as small as 10^{-21}m -- the Zeptouniverse -- in
rare K and B_{s,d} decays, subject to present Delta F=2 constraints and
perturbativity. We focus in particular on a heavy Z' gauge boson. If restricted
to purely LH or RH Z' couplings to quarks, we find that rare K decays, in
particular KL-> pi^0 nu nubar and K^+->pi^+ nu nubar, allow us to probe the
Zeptouniverse. On the other hand rare B_s and B_d decays, which receive
stronger Delta F=2 constraints, allow us to reach about 15 TeV. Allowing for
both LH and RH couplings a loosening of the Delta F=2 constraints is possible,
and we find that the maximal values of M_Z' at which NP effects that are
consistent with perturbative couplings could be found are approximately 2000
TeV for K decays and 160 TeV for rare B_{s,d} decays. Finally we present a
simple idea for an indirect determination of M_Z' that could be realised at the
next linear e^+e^- or mu^+ mu^- collider and with future precise flavour data.Comment: 43 pages, 10 figures, 6 tables; new section on the role of heavy
neutral scalars in reaching Zeptouniverse added; clarifying comments and
references adde
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