61 research outputs found
Fitting Neutrino Physics with a U(1)_R Lepton Number
We study neutrino physics in the context of a supersymmetric model where a
continuous R-symmetry is identified with the total Lepton Number and one
sneutrino can thus play the role of the down type Higgs. We show that
R-breaking effects communicated to the visible sector by Anomaly Mediation can
reproduce neutrino masses and mixing solely via radiative contributions,
without requiring any additional degree of freedom. In particular, a relatively
large reactor angle (as recently observed by the Daya Bay collaboration) can be
accommodated in ample regions of the parameter space. On the contrary, if the
R-breaking is communicated to the visible sector by gravitational effects at
the Planck scale, additional particles are necessary to accommodate neutrino
data.Comment: 19 pages, 3 figures; v2: references added, constraints updated,
overall conclusions unchange
"L = R" - U(1) R as the origin of leptonic 'RPV'
A classification of phenomenologically interesting supersymmetric extensions of the Standard-Model with a U(1) R symmetry is presented. Some of these are consistent with subsets of leptonic or baryonic "R-parity violating" (RPV) operators, thereby providing a natural motivation for them. We then focus on a particular class of models in which the U(1) R symmetry coincides with lepton number when restricted to the SM sector. In this case, the extension of lepton number to the superpartners is "non-standard", implying, in particular, the existence of the leptonic RPV operators LLE c and LQD c, and a vacuum structure where one of the left-handed sneutrinos acquires a significant vacuum-expectation-value, while not being constrained by neutrino mass bounds. The model can be naturally consistent with bounds from electroweak precision measurements and flavor-changing processes. It can also easily accommodate the recently measured Higgs mass due to the existence of a scalar triplet that couples to the Higgs with an order one coupling, with only moderate fine-tuning. The phenomenology is rather rich and distinctive, with features such as heavy-but-natural Dirac gauginos, relaxed bounds on squarks, resonant slepton/sneutrino production, lepto-quark signals, as well as an interesting connection to neutrino physics arising from R-breaking. The broad qualitative features are discussed in this paper, with a more detailed phenomenological study carried out in a companion paper [1]
R-parity violation in SU(5)
We show that judiciously chosen R-parity violating terms in the minimal
renormalizable supersymmetric SU(5) are able to correct all the
phenomenologically wrong mass relations between down quarks and charged
leptons. The model can accommodate neutrino masses as well. One of the most
striking consequences is a large mixing between the electron and the Higgsino.
We show that this can still be in accord with data in some regions of the
parameter space and possibly falsified in future experiments.Comment: 30 pages, 1 figure. Revised version. To appear in JHE
US Cosmic Visions: New Ideas in Dark Matter 2017: Community Report
This white paper summarizes the workshop "U.S. Cosmic Visions: New Ideas in
Dark Matter" held at University of Maryland on March 23-25, 2017.Comment: 102 pages + reference
Dirac gauginos and unification in F-theory
Supersymmetric models in which the gauginos acquire Dirac masses, rather than
Majorana masses, offer an appealing alternative to the minimal supersymmetric
standard model, especially in the light of the bounds set on superpartner
masses by the 2011 LHC data. Dirac gauginos require the presence of chiral
multiplets in the adjoint representation of the gauge group, and the
realisation of such scenarios in F-theory is the subject of this paper. The
chiral adjoints drastically alter the usual picture of gauge coupling
unification, but this is disturbed anyway in F-theory models with non-trivial
hypercharge flux. The interplay between these two factors is explored, and it
is found for example that viable F-theory unification can be achieved at around
the reduced Planck scale, if there is an extra vector-like pair of singlet
leptons with TeV-scale mass. I then discuss the conditions which must be
satisfied by the geometry and hypercharge flux of an F-theory model with Dirac
gauginos. One nice possibility is for the visible sector to be localised on a
K3 surface, and this is discussed in some detail. Finally, I describe how to
achieve an unbroken discrete R-symmetry in such compactifications, which is an
important ingredient in many models with Dirac gauginos, and write down a
simple example which has adjoint chiral multiplets, an appropriate R-symmetry,
and allows for viable breaking of SU(5) by hypercharge flux.Comment: 25 pages, 4 figures. v2: Minor changes; references added. v3: Section
4 modified and expanded; other minor change
The CLIC Potential for New Physics
The Compact Linear Collider (CLIC) is a mature option for the future of high
energy physics. It combines the benefits of the clean environment of
colliders with operation at high centre-of-mass energies, allowing to probe
scales beyond the reach of the Large Hadron Collider (LHC) for many scenarios of new physics. This places the CLIC project at a privileged spot in between the precision and energy frontiers, with capabilities that will significantly extend knowledge on both fronts at the end of the LHC era. In this report we review and revisit the potential of CLIC to search, directly and indirectly, for physics beyond the Standard Model
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