106 research outputs found
Examining a right-handed quark mixing matrix with -tags at the LHC
Encouraged by a hint in a search for right-handed bosons at the LHC, we
investigate whether the unitarity of a right-handed quark mixing matrix and the
equality of the left- and right-handed quark mixing matrices could be tested at
the LHC. We propose a particular test, involving counting the numbers of
-tags in the final state, and simulate the test at the event level with
Monte-Carlo tools for the forthcoming TeV LHC run. We find that
testing unitarity with 20/fb will be challenging; our test successfully rejects
unitarity if the right-handed quark mixing matrix is non-unitary, but only in
particular cases. On the other hand, our test may provide the first opportunity
to test the unitarity of a right-handed quark mixing matrix and with 3000/fb
severely constrains possible departures from unitarity in the latter. We refine
our previous work, testing the equality of quark mixing matrices, with full
collider simulation. With 20/fb, we are sensitive to mixing angles as small as
, and with 3000/fb, angles as small as , confirming our
preliminary analysis. We briefly investigate testing the unitarity of the SM
CKM matrix with a similar method by studying semileptonic production,
concluding that systematics make it particularly difficult.Comment: 20 pages, 5 figures, matches version to appear in Nuclear Physics
SO(10)-inspired solution to the problem of the initial conditions in leptogenesis
We show that, within SO(10)-inspired leptogenesis, there exists a solution,
with definite constraints on low energy neutrino parameters, able
simultaneously to reproduce the observed baryon asymmetry and to satisfy the
conditions for the independence of the final asymmetry of the initial
conditions (strong thermal leptogenesis). We find that the wash-out of a
pre-existing asymmetry as large as O(0.1) requires: i) reactor mixing angle in
the range \theta_13 = (2 - 20) degrees, in agreement with the experimental
result \theta_13 = (8 - 10) degrees; ii) atmospheric mixing angle in the range
\theta_23 = (16 - 41) degrees, compatible only with current lowest
experimentally allowed values; iii) Dirac phase in the range \delta \simeq
-\pi/2 - \pi/5, with the bulk of the solutions around \delta \simeq -\pi/5 and
such that sign(J_CP)= - sign(\eta_B); iv) neutrino masses m_i normally ordered;
v) lightest neutrino mass in the range m_1 \simeq (15 - 25) meV, corresponding
to \sum_i m_i \simeq (85 - 105) meV; vi) neutrinoless double beta decay
(0\nu\beta\beta) effective neutrino mass m_ee \simeq 0.8 m_1. All together this
set of predictive constraints characterises the solution quite distinctively,
representing a difficultly forgeable, fully testable, signature. In particular,
the condition m_ee \simeq 0.8 m_1 \simeq 15 meV can be tested by cosmological
observations and (ultimately) by 0\nu\beta\beta experiments. We also discuss
different aspects such as theoretical uncertainties, stability under variation
of the involved parameters, form of the orthogonal and RH neutrino mixing
matrices.Comment: 44 pages, 8 figures; v3: typos corrected, matches NPB versio
Phase transition and gravitational wave phenomenology of scalar conformal extensions of the Standard Model
Thermal corrections in classically conformal models typically induce a strong
first-order electroweak phase transition, thereby resulting in a stochastic
gravitational wave background that could be detectable at gravitational wave
observatories. After reviewing the basics of classically conformal scenarios,
in this paper we investigate the phase transition dynamics in a thermal
environment and the related gravitational wave phenomenology within the
framework of scalar conformal extensions of the Standard Model. We find that
minimal extensions involving only one additional scalar field struggle to
reproduce the correct phase transition dynamics once thermal corrections are
accounted for. Next-to-minimal models, instead, yield the desired electroweak
symmetry breaking and typically result in a very strong gravitational wave
signal.Comment: 9 pages and 7 figures. Minor changes to match the published versio
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