261 research outputs found
Semi-inclusive hadronic B decays as null tests of the Standard Model
We propose a new set of observables that can be used as experimental null
tests of the Standard Model in charged and neutral B decays. The CP asymmetries
in hadronic decays of charged B mesons into inclusive final states containing
at least one of the following mesons: K_{S,L}, eta', c\bar c bound states or
neutral K^* or D mesons, for all of which a U-spin rotation is equivalent to a
CP conjugation, are CKM suppressed and furthermore vanish in the exact U-spin
limit. We show how this reduces the theoretical error by using Soft Collinear
Effective Theory to calculate the CP asymmetries for K_{S,L} X_{s+d}, K^*
X_{s+d} and eta' X_{s+d} final states in the endpoint region. For these CP
asymmetries only the flavor and not the charge of the decaying B meson needs to
be tagged up to corrections of NLO in 1/m_b, making the measurements more
accessible experimentally.Comment: 8 pages, significantly expanded after the observation that both
neutral and charged B decays can be used, calculation for decays involving
eta' adde
The impact of SuperB on flavour physics
This report provides a succinct summary of the physics programme of SuperB,
and describes that potential in the context of experiments making measurements
in flavour physics over the next 10 to 20 years. Detailed comparisons are made
with Belle II and LHCb, the other B physics experiments that will run in this
decade. SuperB will play a crucial role in defining the landscape of flavour
physics over the next 20 years.Comment: 20 pages, 6 figure
Renormalizability of the Dynamical Two-Form
A proof of renormalizability of the theory of the dynamical non-Abelian
two-form is given using the Zinn-Justin equation. Two previously unknown
symmetries of the quantum action, different from the BRST symmetry, are needed
for the proof. One of these is a gauge fermion dependent nilpotent symmetry,
while the other mixes different fields with the same transformation properties.
The BRST symmetry itself is extended to include a shift transformation by use
of an anticommuting constant. These three symmetries restrict the form of the
quantum action up to arbitrary order in perturbation theory. The results show
that it is possible to have a renormalizable theory of massive vector bosons in
four dimensions without a residual Higgs boson.Comment: revtex, 35p. additional discussion about the auxiliary vector field
and possible gauge choices, relevant to the question of validity of
perturbative expansion, version to be published in Phys.Rev.
Kaon physics with a high-intensity proton driver
We study opportunities for future high-precision experiments in kaon physics
using a high-intensity proton driver, which could be part of the front-end of a
muon storage ring complex. We discuss in particular the rare decays
, , , and
lepton-flavour violating modes such as and . The
outstanding physics potential and long-term interest of these modes is
emphasized. We review status and prospects of current and planned experiments
for the processes under consideration, and indicate possible improvements and
strategies towards achieving the necessary higher sensitivity. Finally, we
outline the machine requirements needed to perform these high-precision kaon
experiments in the context of a muon storage ring facility.Comment: 26 pages, 12 figures; report of the kaon physics working group for
the ECFA studies on neutrino factory and muon storage rings at CERN, G.
Buchalla (convener); references update
Non-Canonical Perturbation Theory of Non-Linear Sigma Models
We explore the O(N)-invariant Non-Linear Sigma Model (NLSM) in a different
perturbative regime from the usual relativistic-free-field one, by using
non-canonical basic commutation relations adapted to the underlying O(N)
symmetry of the system, which also account for the non-trivial (non-flat)
geometry and topology of the target manifold.Comment: 11 pages, 1 figure, LaTe
Self-Dual Conformal Supergravity and the Hamiltonian Formulation
In terms of Dirac matrices the self-dual and anti-self-dual decomposition of
a conformal supergravity is given and a self-dual conformal supergravity theory
is developed as a connection dynamic theory in which the basic dynamic variabes
include the self-dual spin connection i.e. the Ashtekar connection rather than
the triad. The Hamiltonian formulation and the constraints are obtained by
using the Dirac-Bergmann algorithm.
PACS numbers: 04.20.Cv, 04.20.Fy,04.65.+
Cornering New Physics in b --> s Transitions
We derive constraints on Wilson coefficients of dimension-six effective
operators probing the b --> s transition, using recent improved measurements of
the rare decays Bs --> mu+mu-, B --> K mu+mu- and B --> K* mu+mu- and including
all relevant observables in inclusive and exclusive decays. We consider
operators present in the SM as well as their chirality-flipped counterparts and
scalar operators. We find good agreement with the SM expectations. Compared to
the situation before winter 2012, we find significantly more stringent
constraints on the chirality-flipped coefficients due to complementary
constraints from B --> K mu+mu- and B --> K* mu+mu- and due to the LHCb
measurement of the angular observable S_3 in the latter decay. We also list the
full set of observables sensitive to new physics in the low recoil region of B
--> K* mu+mu-.Comment: 18 pages, 6 figures, 4 tables. v3: typos correcte
Possible Discovery Channel for New Charged Leptons at the LHC
We propose a channel for the possible discovery of new charged leptons at the
Large Hadron Collider. The proposed final state contains three same-sign
leptons, making this new channel practically back- groundless. The method is
illustrated for two different cases: the four-family Standard Model and the
Grand Unified Theory based on the E6 gauge group. An example study taking 250
GeV as the charged lepton mass shows that in both models, about 8 signal events
can be expected at 14 TeV center-of-mass energy with 1 fb^-1 of integrated
luminosity. Although the event yield might not be sufficient for detailed
measurements of the charged lepton properties, it would be sufficient to claim
discovery through a counting experiment.Comment: 8 pages, 4 figures. v2 update includes an estimate of the
backgrounds, consideration of the EW oblique parameters, and minor
improvements. v3 update includes detector acceptance and ttbar backgroun
The Standard Model and its Generalizations in Epstein-Glaser Approach to Renormalization Theory II: the Fermion Sector and the Axial Anomaly
We complete our study of non-Abelian gauge theories in the framework of
Epstein-Glaser approach to renormalization theory including in the model an
arbitrary number of Dirac Fermions. We consider the consistency of the model up
to the third order of the perturbation theory. In the second order we obtain
pure group theoretical relations expressing a representation property of the
numerical coefficients appearing in the left and right handed components of the
interaction Lagrangian. In the third order of the perturbation theory we obtain
the the condition of cancellation of the axial anomaly.Comment: 38 pages, LATEX 2e, extensive rewritting, some errors eliminate
Higher-order non-symmetric counterterms in pure Yang-Mills theory
We analyze the restoration of the Slavnov-Taylor (ST) identities for pure
massless Yang-Mills theory in the Landau gauge within the BPHZL renormalization
scheme with IR regulator. We obtain the most general form of the action-like
part of the symmetric regularized action, obeying the relevant ST identities
and all other relevant symmetries of the model, to all orders in the loop
expansion. We also give a cohomological characterization of the fulfillment of
BPHZL IR power-counting criterion, guaranteeing the existence of the limit
where the IR regulator goes to zero. The technique analyzed in this paper is
needed in the study of the restoration of the ST identities for those models,
like the MSSM, where massless particles are present and no invariant
regularization scheme is known to preserve the full set of ST identities of the
theory.Comment: Final version published in the journa
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