58 research outputs found
Ellipsometric measurements of the refractive indices of linear alkylbenzene and EJ-301 scintillators from 210 to 1000 nm
We report on ellipsometric measurements of the refractive indices of LAB-PPO,
Nd-doped LAB-PPO and EJ-301 scintillators to the nearest +/-0.005, in the
wavelength range 210-1000 nm.Comment: 7 pages, 4 figure
First hint for CP violation in neutrino oscillations from upcoming superbeam and reactor experiments
We compare the physics potential of the upcoming neutrino oscillation
experiments Daya Bay, Double Chooz, NOvA, RENO, and T2K based on their
anticipated nominal luminosities and schedules. After discussing the
sensitivity to theta_{13} and the leading atmospheric parameters, we
demonstrate that leptonic CP violation will hardly be measurable without
upgrades of the T2K and NOvA proton drivers, even if theta_{13} is large. In
the presence of the proton drivers, the fast track to hints for CP violation
requires communication between the T2K and NOvA collaborations in terms of a
mutual synchronization of their neutrino-antineutrino run plans. Even in that
case, upgrades will only discover CP violation in a relatively small part of
the parameter space at the 3 sigma confidence level, while 90% confidence level
hints will most likely be obtained. Therefore, we conclude that a new facility
will be required if the goal is to obtain a significant result with high
probability.Comment: 27 pages, 12 figure
Status and perspectives of short baseline studies
The study of flavor changing neutrinos is a very active field of research. I
will discuss the status of ongoing and near term experiments investigating
neutrino properties at short distances from the source. In the next few years,
the Double Chooz, RENO and Daya Bay reactor neutrino experiments will start
looking for signatures of a non-zero value of the mixing angle
with much improved sensitivities. The MiniBooNE experiment is investigating the
LSND anomaly by looking at both the and
appearance channels. Recent results on
cross section measurements will be discussed briefly.Comment: 6 pages, 2 figures, to appear in the proceedings of the 11th
International Conference on Topics in Astroparticle and Underground Physics
(TAUP 2009), Rome, Italy, 1-5 July 200
Common Origin of Soft mu-tau and CP Breaking in Neutrino Seesaw and the Origin of Matter
Neutrino oscillation data strongly support mu-tau symmetry as a good
approximate flavor symmetry of the neutrino sector, which has to appear in any
viable theory for neutrino mass-generation. The mu-tau breaking is not only
small, but also the source of Dirac CP-violation. We conjecture that both
discrete mu-tau and CP symmetries are fundamental symmetries of the seesaw
Lagrangian (respected by interaction terms), and they are only softly broken,
arising from a common origin via a unique dimension-3 Majorana mass-term of the
heavy right-handed neutrinos. From this conceptually attractive and simple
construction, we can predict the soft mu-tau breaking at low energies, leading
to quantitative correlations between the apparently two small deviations
\theta_{23} - 45^o and \theta_{13} - 0^o. This nontrivially connects the
on-going measurements of mixing angle \theta_{23} with the upcoming
experimental probes of \theta_{13}. We find that any deviation of \theta_{23} -
45^o must put a lower limit on \theta_{13}. Furthermore, we deduce the low
energy Dirac and Majorana CP violations from a common soft-breaking phase
associated with mu-tau breaking in the neutrino seesaw. Finally, from the soft
CP breaking in neutrino seesaw we derive the cosmological CP violation for the
baryon asymmetry via leptogenesis. We fully reconstruct the leptogenesis
CP-asymmetry from the low energy Dirac CP phase and establish a direct link
between the cosmological CP-violation and the low energy Jarlskog invariant. We
predict new lower and upper bounds on the \theta_{13} mixing angle, 1^o <
\theta_{13} < 6^o. In addition, we reveal a new hidden symmetry that dictates
the solar mixing angle \theta_12 by its group-parameter, and includes the
conventional tri-bimaximal mixing as a special case, allowing deviations from
it.Comment: 60pp, JCAP in Press, v2: only minor stylistic refinements (added Daya
Bay's future sensitivity in Figs.2+8, shortened some eqs, added new
Appendix-A and some references), comments are welcome
NLO corrections to ultra-high energy neutrino-nucleon scattering, shadowing and small x
We reconsider the Standard Model interactions of ultra-high energy neutrinos
with matter. The next to leading order QCD corrections are presented for
charged-current and neutral-current processes. Contrary to popular
expectations, these corrections are found to be quite substantial, especially
for very large (anti-) neutrino energies. Hence, they need to be taken into
account in any search for new physics effects in high-energy neutrino
interactions. In our extrapolation of the parton densities to kinematical
regions as yet unexplored directly in terrestrial accelerators, we are guided
by double asymptotic scaling in the large Q^2 and small Bjorken x region and to
models of saturation in the low Q^2 and low x regime. The sizes of the
consequent uncertainties are commented upon. We also briefly discuss some
variables which are insensitive to higher order QCD corrections and are hence
suitable in any search for new physics.Comment: 21 pages, LaTeX2e, uses JHEP3.cls (included), 8 ps files for figures
published versio
Grand Unification of Flavor Mixings
An origin of flavor mixings in quark and lepton sectors is still a mystery,
and a structure of the flavor mixings in lepton sector seems completely
different from that of quark sector. In this letter, we point out that the
flavor mixing angles in quark and lepton sectors could be unified at a high
energy scale, when neutrinos are degenerate. It means that a minimal flavor
violation at a high energy scale can induce a rich variety of flavor mixings in
quark and lepton sectors at a low energy scale through quantum corrections.Comment: 5 pages, 12 figures, references added, version to appear in EP
On the capture of dark matter by neutron stars
We calculate the number of dark matter particles that a neutron star
accumulates over its lifetime as it rotates around the center of a galaxy, when
the dark matter particle is a self-interacting boson but does not
self-annihilate. We take into account dark matter interactions with baryonic
matter and the time evolution of the dark matter sphere as it collapses within
the neutron star. We show that dark matter self-interactions play an important
role in the rapid accumulation of dark matter in the core of the neutron star.
We consider the possibility of determining an exclusion region of the parameter
space for dark matter mass and dark matter interaction cross sections based on
the observation of old neutron stars with strong dark matter self-interactions.
We show that for a dark matter density of GeV/cm and dark matter
mass less than approximately 10 GeV, there is a potential exclusion
region for dark matter interactions with nucleons that is three orders of
magnitude more stringent than without self-interactions. The potential
exclusion region for dark matter self-interaction cross sections is many orders
of magnitude stronger than the current Bullet Cluster limit. For example, for
high dark matter density regions, we find that for GeV when the
dark matter interaction cross section with the nucleons ranges from
cm to cm, the dark matter
self-interaction cross section limit is cm,
which is about ten orders of magnitude stronger than the Bullet Cluster limit.Comment: 12 pages, 9 figures, v2. change in treatment of dark matter collapse
in neutron star, conclusions changed; v3. minor revisions of text for
clarification, added references, v4. version accepted for publication in JCA
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