10,416 research outputs found
The International Axion Observatory (IAXO)
The International Axion Observatory (IAXO) is a new generation axion
helioscope aiming at a sensitivity to the axion-photon coupling of a few
10 GeV, i.e. 1 - 1.5 orders of magnitude beyond the one currently
achieved by CAST. The project relies on improvements in magnetic field volume
together with extensive use of x-ray focusing optics and low background
detectors, innovations already successfully tested in CAST. Additional physics
cases of IAXO could include the detection of electron-coupled axions invoked to
solve the white dwarfs anomaly, relic axions, and a large variety of more
generic axion-like particles (ALPs) and other novel excitations at the
low-energy frontier of elementary particle physics. This contribution is a
summary of our paper [1] to which we refer for further details.Comment: 4 pages, 2 figures. To appear in the proceedings of the 7th Patras
Workshop on Axions, WIMPs and WISPs, Mykonos, Greece, 201
Determining weak phases from B->J/Psi P decays
The decay B -> J/Psi K_S remains the most important source of information for
the B_d mixing phase, determined by the CKM angle beta in the standard model.
When aiming at a precision appropriate for present and coming high luminosity
colliders, the corresponding hadronic matrix elements are a major obstacle, as
their precise calculation is still not feasible with existing methods. Flavour
symmetries offer a possibility to extract them from data, however again with
limited precision. In this article, we propose a framework to take subleading
contributions in B_{u,d,s} -> J/Psi P decays into account, P=(pi,K,(eta_8)),
using an SU(3) analysis, together with the leading corrections to the symmetry
limit. This allows for a model-independent extraction of the B_d mixing phase
adequate for coming high precision data, and additionally yields information on
possible New Physics contributions in these modes. We find the penguin-induced
correction to be small, |Delta S|<~0.01, a limit which can be improved with
coming data on CP asymmetries and branching ratios. Finally, the sensitivity on
the CKM angle gamma from these modes is critically examined, yielding a less
optimistic picture than previously envisaged.Comment: 15+6 pages, 6 figures. Minor changes to v1, conclusions unchanged.
Version accepted for publication in PR
Inclusive Displaced Vertex Searches for Heavy Neutral Leptons at the LHC
The inclusion of heavy neutral leptons to the Standard Model particle content
could provide solutions to many open questions in particle physics and
cosmology. The modification of the charged and neutral currents from
active-sterile mixing of neutral leptons can provide novel signatures in
Standard Model processes. We revisit the displaced vertex signature that could
occur in collisions at the LHC via the decay of heavy neutral leptons with
masses of a few GeV emphasizing the implications of flavor, kinematics,
inclusive production and number of these extra neutral fermions. We study in
particular the implication on the parameter space sensitivity when all mixings
to active flavors are taken into account. We also discuss alternative cases
where the new particles are produced in a boosted regime.Comment: 24 pages, 10 figures. Extended analysis. Published versio
Stationary Mixing Bandits
We study the bandit problem where arms are associated with stationary
phi-mixing processes and where rewards are therefore dependent: the question
that arises from this setting is that of recovering some independence by
ignoring the value of some rewards. As we shall see, the bandit problem we
tackle requires us to address the exploration/exploitation/independence
trade-off. To do so, we provide a UCB strategy together with a general regret
analysis for the case where the size of the independence blocks (the ignored
rewards) is fixed and we go a step beyond by providing an algorithm that is
able to compute the size of the independence blocks from the data. Finally, we
give an analysis of our bandit problem in the restless case, i.e., in the
situation where the time counters for all mixing processes simultaneously
evolve
On Direct Verification of Warped Hierarchy-and-Flavor Models
We consider direct experimental verification of warped models, based on the
Randall-Sundrum (RS) scenario, that explain gauge and flavor hierarchies,
assuming that the gauge fields and fermions of the Standard Model (SM)
propagate in the 5D bulk. Most studies have focused on the bosonic Kaluza Klein
(KK) signatures and indicate that discovering gauge KK modes is likely
possible, yet challenging, while graviton KK modes are unlikely to be
accessible at the LHC, even with a luminosity upgrade. We show that direct
evidence for bulk SM fermions, {\it i.e.} their KK modes, is likely also beyond
the reach of a luminosity-upgraded LHC. Thus, neither the spin-2 KK graviton,
the most distinct RS signal, nor the KK SM fermions, direct evidence for bulk
flavor, seem to be within the reach of the LHC. We then consider hadron
colliders with 21, 28, and 60 TeV. We find that discovering the
first KK modes of SM fermions and the graviton typically requires the Next
Hadron Collider (NHC) with TeV and
ab of integrated luminosity. If the LHC yields hints of these warped
models, establishing that Nature is described by them, or their 4D CFT duals,
requires an NHC-class machine in the post-LHC experimental program.Comment: Revtex4, 21 pages, 11 figure
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