3,233 research outputs found
New U(1) Gauge Symmetry of Quarks and Leptons
Instead of anchoring the seesaw mechanism with the conventional heavy
right-handed neutrino singlet, a small Majorana neutrino mass may be obtained
just as well with the addition of a heavy triplet of leptons per family to the
minimal standard model of particle interactions. The resulting model is shown
to have the remarkable property of accommodating a new U(1) symmetry which is
anomaly-free and may thus be gauged. There are many possible phenomenological
consequences of this proposal which may be already relevant in explaining one
or two recent potential experimental discrepancies.Comment: minor word changes, to appear in MPL
Branching Ratio and CP Asymmetry of B_s \to K^*_0(1430)\pi Decays in the PQCD Approach
In the two-quark model supposition for , the branching ratios
and the direct CP-violating asymmetries for decays are studied by employing the
perturbative QCD factorization approach. We find that although these two decays
are both tree-dominated, the ratio of their penguin to tree contributions are
very different: there is only a few percent for the decay , while about 37% in scenario I, even 51% in scenario II
for the decay . It results that these two
decays have very different values in the branching ratios and the direct CP
asymmetries. The branching ratio of the decay is at the order of , and its direct CP asymmetry
is about (20-30)%. While for the decay , its
direct CP-violating asymmetry is very large and about 90%, but it is difficult
to measure it, because the branching ratio for this channel is small and only
order.Comment: 8pages, 2figure
Study of f_0(980) and f_0(1500) from B_s \to f_0(980)K, f_0(1500)K Decays
In this paper, we calculate the branching ratios and CP-violating asymmetries
for \bar B^0_s \to f_0(980)K, f_0(1500)K within Perturbative QCD approach based
on k_T factorization. If the mixing angle falls into the range of
25^\circ<\theta<40^\circ, the branching ratio of \bar B^0_s\to f_0(980)K is
2.0\times 10^{-6}<{\cal B}(\bar B^0_s\to f_0(980)K)<2.6\times 10^{-6}, while
lies in the range of 140^\circ<\theta<165^\circ, {\cal B}(\bar
B^0_s\to f_0(980)K) is about 6.5\times 10^{-7}. As to the decay {\cal B}(\bar
B^0_s\to f_0(1500)K), when the mixing scheme \mid f_0(1500)>=0.84\mid s\bar
s>-0.54\mid n\bar n> for f_0(1500) is used, it is difficult to determine which
scenario is more preferable than the other one from the branching ratios for
these two scenarios, because they are both close to 1.0\times10^{-6}. But there
exists large difference in the form factor F^{\bar B_s^0\to f_0(1500)} for two
scenarios.Comment: 14 pages, 3 figures, submitted to J. Phys.
Floquet Energies and Quantum Hall Effect in a Periodic Potential
The Quantum Hall Effect for free electrons in external periodic field is
discussed without using the linear response approximation. We find that the
Hall conductivity is related in a simple way to Floquet energies (associated to
the Schroedinger equation in the co-moving frame). By this relation one can
analyze the dependence of the Hall conductivity from the electric field.
Sub-bands can be introduced by the time average of the expectation value of the
Hamiltonian on the Floquet states. Moreover we prove previous results in form
of sum rules as, for instance: the topological character of the Hall
conductivity (being an integer multiple of e^2/h), the Diofantine equation
which constrains the Hall conductivity by the rational number which measures
the flux of the magnetic field through the periodicity cell. The Schroedinger
equation fixes in a natural way the phase of the wave function over the reduced
Brillouin zone: thus the topological invariant providing the Hall conductivity
can be evaluated numerically without ambiguity.Comment: LaTex (revtex), 18 pages, 10 figures in .eps using epsf.sty. Changes
in eq. (3.2). References adde
Open charm scenarios
We discuss possibilities of identifying open charm effects in direct
production processes, and propose that direct evidence for the open charm
effects can be found in . A unique feature with this
process is that the open channel is located in a relatively
isolated energy, i.e. GeV, which is sufficiently far away from the
known charmonia and . Due to the dominance of the
isospin-0 component at the charmonium energy region, an enhanced
model-independent cusp effect between the thresholds of
and can be highlighted. An energy scan over this energy
region in the annihilation reaction can help us to understand the
nature of X(3900) recently observed by Belle Collaboration in , and establish the open charm effects as an important
non-perturbative mechanism in the charmonium energy region.Comment: 6 pages, Proceeding contribution to the Rutherford Centennial
Conference, Aug. 8-12, 2011, Manchester, U.
Non-functional immunoglobulin G transcripts in a case of hyper-immunoglobulin M syndrome similar to type 4
86% of immunoglobulin G (IgG) heavy-chain gene transcripts were found to be non-functional in the peripheral blood B cells of a patient initially diagnosed with common variable immunodeficiency, who later developed raised IgM, whereas no non-functionally rearranged transcripts were found in the cells of seven healthy control subjects. All the patient's IgM heavy-chain and κ light-chain transcripts were functional, suggesting that either non-functional rearrangements were being selectively class-switched to IgG, or that receptor editing was rendering genes non-functional after class-switching. The functional γ-chain sequences showed a normal rate of somatic hypermutation while non-functional sequences contained few somatic mutations, suggesting that most came from cells that had no functional gene and therefore were not receiving signals for hypermutation. However, apoptosis of peripheral blood lymphocytes was not impaired. No defects have been found in any of the genes currently known to be responsible for hyper-IgM syndrome but the phenotype fits best to type 4
eta_c production at the Large Hadron Collider
We have studied the production of the 1S_0 charmonium state, eta_c, at the
Large Hadron Collider (LHC) in the framework of Non-Relativistic Quantum
Chromodynamics (NRQCD) using heavy-quark symmetry. We find that NRQCD predicts
a large production cross-section for this resonance at the LHC even after
taking account the small branching ratio of eta_c into two photons. We show
that it will be possible to test NRQCD through its predictions for eta_c, with
the statistics that will be achieved at the early stage of the LHC, running at
a center of mass energy of 7 TeV with an integrated luminosity of 100 pb^{-1}Comment: 8 pages, 2 figure
The CDF dijet excess from intrinsic quarks
The CDF collaboration reported an excess in the production of two jets in
association with a . We discuss constraints on possible new particle state
interpretations of this excess. The fact of no statistically significant
deviation from the SM expectation for {+dijet} events in CDF data disfavors
the new particle explanation. We show that the nucleon intrinsic strange quarks
provide an important contribution to the boson production in association
with a single top quark production. Such {+t} single top quark production
can contribute to the CDF {+dijet} excess, thus the nucleon intrinsic quarks
can provide a possible explanation to the CDF excess in {+dijet} but not in
{+dijet} events.Comment: 4 latex pages, 1 figure. Version for journal publicatio
Composition of the Pseudoscalar Eta and Eta' Mesons
The composition of the eta and eta' mesons has long been a source of
discussion and is of current interest with new experimental results appearing.
We investigate what can be learnt from a number of different processes: V to P
gamma and P to V gamma (V and P are light vector and pseudoscalar mesons
respectively), P to gamma gamma, J/psi,psi' to P gamma, J/psi,psi' to P V, and
chi_{c0,2} to PP. These constrain the eta-eta' mixing angle to a consistent
value, phi approx 42 degrees; we find that the c cbar components are lesssim 5%
in amplitude. We also find that, while the data hint at a small gluonic
component in the eta', the conclusions depend sensitively on unknown form
factors associated with exclusive dynamics. In addition, we predict BR(psi' to
eta' gamma) approx 1 10^{-5} and BR(chi_{c0} to eta eta') approx 2 10^{-5} - 1
10^{-4}. We provide a method to test the mixing using chi_{c2} to eta eta, eta'
eta', and eta eta' modes and make some general observations on chi_{c0,2}
decays. We also survey the semileptonic and hadronic decays of bottom and
charmed mesons and find some modes where the mixing angle can be extracted
cleanly with the current experimental data, some where more data will allow
this, and some where a more detailed knowledge of the different amplitudes is
required.Comment: 34 pages, 11 figures. v2: version published in JHEP, added
substantial section on B and D meson electroweak decays, added comment on
psi' to eta(')/eta_c gamma, Figs 5 and 6 split and made clearer, added
references, other minor revisions which don't change conclusion
Transitions in Family-dependent Models
We analyze flavor-changing-neutral-current (FCNC) effects in the
transitions that are induced by family non-universal gauge symmetries.
After systematically developing the necessary formalism, we present a
correlated analysis for the processes. We adopt a
model-independent approach in which we only require family-universal charges
for the first and second generations and small fermion mixing angles. We
analyze the constraints on the resulting parameter space from
mixing and the time-dependent CP asymmetries of the penguin-dominated decays. Our results indicate that the
currently observed discrepancies in some of these modes with respect to the
Standard Model predictions can be consistently accommodated within this general
class of models.Comment: 36 pages, 11 figure
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