23 research outputs found
Dirac neutrinos and anomaly-free discrete gauge symmetries
Relying on Dirac neutrinos allows an infinity of anomaly-free discrete gauge
symmetries to be imposed on the Supersymmetric Standard Model, some of which
are GUT-compatible.Comment: 24 pages, minor changes, existence of flipped discrete gauge
symmetries is pointed ou
What is the Discrete Gauge Symmetry of the MSSM?
We systematically study the extension of the Supersymmetric Standard Model
(SSM) by an anomaly-free discrete gauge symmetry Z_N. We extend the work of
Ibanez and Ross with N=2,3 to arbitrary values of N. As new fundamental
symmetries, we find four Z_6, nine Z_9 and nine Z_18. We then place three
phenomenological demands upon the low-energy effective SSM: (i) the presence of
the mu-term in the superpotential, (ii) baryon-number conservation upto
dimension-five operators, and (iii) the presence of the see-saw neutrino mass
term LHLH. We are then left with only two anomaly-free discrete gauge
symmetries: baryon-triality, B_3, and a new Z_6, which we call proton-hexality,
P_6. Unlike B_3, P_6 prohibits the dimension-four lepton-number violating
operators. This we propose as the discrete gauge symmetry of the Minimal SSM,
instead of R-parity.Comment: Typo in item 2 below Eq.(6.9) corrected (wrong factor of "3"); 27
pages, 5 table
Supersymmetric Jarlskog Invariants: the Neutrino Sector
We generalize the notion of the Jarlskog invariant to supersymmetric models
with right--handed neutrinos. This allows us to formulate basis--independent
necessary and sufficient conditions for CP conservation in such models.Comment: 10 pages, no figure
Bounds on Broken R-Parity from Leptonic Meson Decays
Investigating leptonic decays of pi^-, K^-, B^-, pi^0, K_L^0, B_s^0 we
present new bounds on some products of two R-parity violating coupling
constants. For mesons of a similar structure but so far poor experimental data
we give the corresponding formulae, to be used in the future.Comment: Latex, 15 pages, 1 figure; final version which appeared in Phys.Rev.
Probing the Planck Scale with Proton Decay
We advocate the idea that proton decay may probe physics at the Planck scale
instead of the GUT scale. This is possible because supersymmetric theories have
dimension-5 operators that can induce proton decay at dangerous rates, even
with R-parity conservation. These operators are expected to be suppressed by
the same physics that explains the fermion masses and mixings. We present a
thorough analysis of nucleon partial lifetimes in models with a string-inspired
anomalous U(1)_X family symmetry which is responsible for the fermionic mass
spectrum as well as forbidding R-parity violating interactions. Protons and
neutrons can decay via R-parity conserving non-renormalizable superpotential
terms that are suppressed by the Planck scale and powers of the Cabibbo angle.
Many of the models naturally lead to nucleon decay near present limits without
any reference to grand unification.Comment: 11 pages,4 figures. Revised to drop the options y=-6, -7 that are not
phenomenologically viable anyway, following the revision of hep-ph/0312012
this work is based on. Conclusions unchange
String Inspired Z' Model With Stable Proton and Light Neutrino Masses
Grand unification, and its incarnation in the form of heterotic-string
unification, are the only extensions of the Standard Model that are rooted in
the structure of the Standard Model itself. In this context, it was proposed
that the exclusiveness of proton stability and suppression of neutrino masses
necessitates the existence of an additional U(1)_Z' symmetry, which is of
non-GUT origin and remains unbroken down to intermediate, or low, energies.
Realistic string models frequently give rise to non-GUT U(1) symmetries, which
arise from the flavor symmetries in the models. In this paper we demonstrate in
a string-inspired toy model that such a stringy Z' can indeed guarantee proton
longevity and viable phenomenology in the neutrino sector, as well as in the
quark and charged lepton sectors.Comment: 20 pages. Standard LaTex. Version to appear in NP
Baryon Triality and Neutrino Masses from an Anomalous Flavor U(1)
We construct a concise U(1)_X Froggatt-Nielsen model in which baryon
triality, a discrete gauge Z_3 symmetry, arises from U(1)_X breaking. The
proton is thus stable, however, R-parity is violated. With the proper choice of
U(1)_X charges we can obtain neutrino masses and mixings consistent with an
explanation of the atmospheric and solar neutrino anomalies in terms of
neutrino oscillations, with no right-handed neutrinos required. The only mass
scale apart from M_grav is m_3/2 ~ m_soft.Comment: matches published version, typos corrected, references added, 54
pages, 3 figures, 5 table
Proton Hexality from an Anomalous Flavor U(1) and Neutrino Masses - Linking to the String Scale
We devise minimalistic gauged U(1)_X Froggatt-Nielsen models which at
low-energy give rise to the recently suggested discrete gauge Z_6 symmetry,
proton hexality, thus stabilizing the proton. Assuming three generations of
right-handed neutrinos, with the proper choice of X-charges, we obtain viable
neutrino masses. Furthermore, we find scenarios such that no X-charged hidden
sector superfields are needed, which from a bottom-up perspective allows the
calculation of g_string, g_X and G_SM's Kac-Moody levels. The only mass scale
apart from M_grav is m_soft.Comment: 32 pages, 8 tables, references updated, matches published versio
Exotic particles below the TeV from low scale flavour theories
A flavour gauge theory is observable only if the symmetry is broken at
relatively low energies. The intrinsic parity-violation of the fermion
representations in a flavour theory describing quark, lepton and higgsino
masses and mixings generically requires anomaly cancellation by new fermions.
Benchmark supersymmetric flavour models are built and studied to argue that: i)
the flavour symmetry breaking should be about three orders of magnitude above
the higgsino mass, enough also to efficiently suppress FCNC and CP violations
coming from higher-dimensional operators; ii) new fermions with exotic decays
into lighter particles are typically required at scales of the order of the
higgsino mass.Comment: 19 pages, references added, one comment and one footnote added,
results unchange