374 research outputs found
Heavy-meson physics and flavour violation with a single generation
We study flavour-violating processes which involve heavy B- and D-mesons and
are mediated by Kaluza-Klein modes of gauge bosons in a previously suggested
model where three generations of the Standard Model fermions originate from a
single generation in six dimensions. We find the bound on the size R of the
extra spatial dimensions 1/R>3.3 TeV, which arises from the three-body decay
B_s to K mu e. Due to the still too low statistics this bound is much less
stringent than the constraint arising from K to mu e, 1/R>64 TeV, which was
found in a previous work (Frere et al., JHEP, 2003). Nevertheless, we argue
that a clear signature of the model would be an observation of K to mu e and
B_s to K mu e decays without observations of other flavour and lepton number
changing processes at the same precision level.Comment: 15 page
Fermionic zero modes in gauge and gravity backgrounds On
In this note we study fermionic zero modes in gauge and gravity backgrounds
taking a two dimensional compact manifold as extra dimensions. The result
is that there exist massless Dirac fermions which have normalizable zero modes
under quite general assumptions about these backgrounds on the bulk. Several
special cases of gauge background on the torus are discussed and some simple
fermionic zero modes are obtained.Comment: 8 pages, no figures, v2: more references, accepted by Mod.Phys.Lett.
See-saw neutrino masses and large mixing angles in the vortex background on a sphere
In the vortex background on a sphere, a single 6-dimensional fermion family
gives rise to 3 zero-modes in the 4-dimensional point of view, which may
explain the replication of families in the Standard Model. Previously, it had
been shown that realistic hierarchical mass and mixing patterns can be
reproduced for the quarks and the charged leptons. Here, we show that the
addition of a single heavy 6-dimensional field that is gauge singlet, unbound
to the vortex, and embedded with a bulk Majorana mass enables to generate 4D
Majorana masses for the light neutrinos through the see-saw mechanism. The
scheme is very predictive. The hierarchical structure of the fermion zero-modes
leads automatically to an inverted pseudo-Dirac mass pattern, and always
predicts one maximal angle in the neutrino see-saw matrix. It is possible to
obtain a second large mixing angle from either the charged lepton or the
neutrino sector, and we demonstrate that this model can fit all observed data
in neutrino oscillations experiments. Also, U_{e3} is found to be of the order
~0.1.Comment: 23 pages, 1 figur
BRS Cedro e BRS Jatobá: cultivares de algodoeiro herbáceo recomendadas para os cerrados do Meio-Norte do Brasil.
bitstream/CPAMN-2009-09/18166/1/CT155.pd
FCNC in left-right symmetric theories and constraints on the right-handed scale
We revise the limits on the FCNC higgses in manifestly left-right symmetric
theories. It is shown that the combination of the Kobayashi-Maskawa
CP-violation with the tree level higgs exchange gives very large
contribution to the CP-violating parameter. It leads to the new
strong constraint on the FCNC higgs mass, M>50- 100 TeV, enhanced by factor of
the order . Being addressed to the supersymmetric left-right
models, FCNC problem requires both right-handed scale and supersymmetric mass
parameters be heavier than 50 TeV for . The most relaxed case
corresponds to where right-handed scale can be of the
order of few TeV.Comment: 11 pages, latex, 3 figure
Development and validation of the BRIGHTLIGHT Survey, a patient-reported experience measure for young people with cancer
BACKGROUND: Patient experience is increasingly used as an indicator of high quality care in addition to more traditional clinical end-points. Surveys are generally accepted as appropriate methodology to capture patient experience. No validated patient experience surveys exist specifically for adolescents and young adults (AYA) aged 13-24 years at diagnosis with cancer. This paper describes early work undertaken to develop and validate a descriptive patient experience survey for AYA with cancer that encompasses both their cancer experience and age-related issues. We aimed to develop, with young people, an experience survey meaningful and relevant to AYA to be used in a longitudinal cohort study (BRIGHTLIGHT), ensuring high levels of acceptability to maximise study retention. METHODS: A three-stage approach was employed: Stage 1 involved developing a conceptual framework, conducting literature/Internet searches and establishing content validity of the survey; Stage 2 confirmed the acceptability of methods of administration and consisted of four focus groups involving 11 young people (14-25 years), three parents and two siblings; and Stage 3 established survey comprehension through telephone-administered cognitive interviews with a convenience sample of 23 young people aged 14-24 years. RESULT: Stage 1: Two-hundred and thirty eight questions were developed from qualitative reports of young people's cancer and treatment-related experience. Stage 2: The focus groups identified three core themes: (i) issues directly affecting young people, e.g. impact of treatment-related fatigue on ability to complete survey; (ii) issues relevant to the actual survey, e.g. ability to answer questions anonymously; (iii) administration issues, e.g. confusing format in some supporting documents. Stage 3: Cognitive interviews indicated high levels of comprehension requiring minor survey amendments. CONCLUSION: Collaborating with young people with cancer has enabled a survey of to be developed that is both meaningful to young people but also examines patient experience and outcomes associated with specialist cancer care. Engagement of young people throughout the survey development has ensured the content appropriately reflects their experience and is easily understood. The BRIGHTLIGHT survey was developed for a specific research project but has the potential to be used as a TYA cancer survey to assess patient experience and the care they receive
Enhanced baryon number violation due to cosmological defects with localized fermions along extra dimension
We propose a new scenario of baryon number violation in models with extra
dimensions. In the true vacuum, baryon number is almost conserved due to the
localization mechanism of matter fields, which suppresses the interactions
between quarks and leptons. We consider several types of cosmological defects
in four-dimensional spacetime that shift the center of the localized matter
fields, and show that the magnitudes of the baryon number violating
interactions are well enhanced. Application to baryogenesis is also discussed.Comment: 12pages, latex2e, added references, to appear in PR
Unstable Heavy Majorana Neutrinos and Leptogenesis
We propose a new mechanism producing a non-vanishing lepton number asymmetry,
based on decays of heavy Majorana neutrinos. If they are produced out of
equilibrium, as occurs in preheating scenario, and are superpositions of mass
eigenstates rapidly decaying, their decay rates contains interference terms
provided the mass differences are small compared to widths .
The resulting lepton asymmetry, which is the analogue of the time-integrated CP
asymmetry in system, is found to be proportional to .Comment: 18 pages, latex, revised version to be published in Phys. Rev.
Supersymmetric Relations Among Electromagnetic Dipole Operators
Supersymmetric contributions to all leptonic electromagnetic dipole operators
have essentially identical diagramatic structure. With approximate slepton
universality this allows the muon anomalous magnetic moment to be related to
the electron electric dipole moment in terms of supersymmetric phases, and to
radiative flavor changing lepton decays in terms of small violations of slepton
universality. If the current discrepancy between the measured and Standard
Model values of the muon anomalous magnetic moment is due to supersymmetry, the
current bound on the electron electric dipole moment then implies that the
phase of the electric dipole operator is less than . Likewise
the current bound on decay implies that the fractional
selectron-smuon mixing in the left-left mass squared matrix, \delta m_{\smuon
\selectron}^2 / m_{\slepton}^2, is less than . These relations and
constraints are fairly insensitive to details of the superpartner spectrum for
moderate to large .Comment: Latex, 38 pages, 2 figure
Effects of SO(10) D-Term on Yukawa Unification and Unstable Minima of the Supersymmetric Scalar Potential
We study the effects of SO(10) D-terms on the allowed parameter space (APS)
in models with and Yukawa unifiction. The former is
allowed only for moderate values of the D-term, if very precise ( 5%)
unification is required. Next we constrain the parameter space by looking for
different dangerous directions where the scalar potential may be unbounded from
below (UFB1 and UFB3). The common trilinear coupling plays a significant
role in constraing the APS. For very precise Yukawa unification,
can be probed at the LHC, where
is the common soft breaking mass for the sfermions. Moreover, an
interesting mass hierarchy with very heavy sfermions but light gauginos, which
is strongly disfavoured in models without D-terms, becomes fairly common in the
presence of the D-terms. The APS exhibits interesting characteristics if
is not the same as the soft breaking mass for the Higgs
sector. In unification models with D-terms, the APS consistent with
Yukawa unification and radiative electroweak symmetry breaking, increases as
the UFB1 constraint becomes weaker. However for , a stronger UFB3
condition still puts, for a given , a stringent upper bound on the
common gaugino mass () and a lower bound on for a given
. The effects of sign of on Yukawa unification and UFB
constraints are also discussed.Comment: Plain Latex, 22 pages, 11 figures. Small changes in the abstract, the
pattern of discussion changed signifiantly, no change in the figures and
results, a few new references added, version published in JP
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