18 research outputs found
A Little Higgs Model with Exact Dark Matter Parity
Based on a recent idea by Krohn and Yavin, we construct a little Higgs model
with an internal parity that is not broken by anomalous Wess-Zumino-Witten
terms. The model is a modification of the "minimal moose" models by
Arkani-Hamed et al. and Cheng and Low. The new parity prevents large
corrections to oblique electroweak parameters and leads to a viable dark matter
candidate. It is shown how the complete Standard Model particle content,
including quarks and leptons together with their Yukawa couplings, can be
implemented. Successful electroweak symmetry breaking and consistency with
electroweak precision constraints is achieved for natural paramters choices. A
rich spectrum of new particles is predicted at the TeV scale, some of which
have sizable production cross sections and striking decay signatures at the
LHC.Comment: 25 pp. LaTeX; v2: improved discussion of precision constraints and
references added; v3: summary of model structure added at beginning of sect.
2, version published in JHEP; v4: small correction in Fig.5; v5: correction
to Fig.
Consequences of T-parity breaking in the Littlest Higgs model
In this paper we consider the effects of the T-parity violating anomalous
Wess-Zumino-Witten-Term in the Littlest Higgs model. Apart from tree level
processes, the loop induced decays of the heavy mirror particles into light
standard model fermions lead to a new and rich phenomenology in particular at
breaking scales f below 1 TeV. Various processes are calculated and their
signatures at present and future colliders are discussed. As a byproduct we
find an alternative production mechanism for the Higgs boson.Comment: 30 page
Late energy injection and cosmological constraints in axino dark matter scenarios
Taking into account effects of late energy injection, we examine big bang nucleosynthesis (BBN) constraints on axino dark matter scenarios with long-lived charged sleptons. We calculate 4-body slepton decays into the axino, a lepton, and a quark–antiquark pair since they govern late hadronic energy injection and associated BBN constraints. For supersymmetric hadronic axion models, we present the obtained hadronic BBN constraints and show that they can be more restrictive than the ones associated with catalyzed BBN via slepton-bound-state formation. From the BBN constraints on hadronic and electromagnetic energy release, we find new upper limits on the Peccei–Quinn scale
Phenomenology of the Little Higgs model with X-Parity
In the popular littlest Higgs model, T-parity can be broken by
Wess-Zumino-Witten (WZW) terms induced by a strongly coupled UV completion. On
the other hand, certain models with multiple scalar multiplets (called moose
models) permit the implementation of an exchange symmetry (X-parity) such that
it is not broken by the WZW terms. Here we present a concrete and realistic
construction of such a model. The little Higgs model with X-Parity is a
concrete and realistic implementation of this idea. In this contribution, the
properties of the model are reviewed and the collider phenomenology is
discussed in some detail. We also present new results on the decay properties
and LHC signatures of the light triplet scalars that are predicted by this
model.Comment: 12 pages, to appear in in the proceedings of the International
Workshop on Beyond the Standard Model Physics and LHC Signatures (BSM-LHC)
and of the 17th International Conference on Supersymmetry and the Unification
of Fundamental Interactions (SUSY09), Boston, USA, 2-4 and 5-10 Jun 200
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
Unparticle Searches Through Compton Scattering
We investigate the effects of unparticles on Compton scattering, e gamma -> e
gamma based on a future e^+e^- linear collider such as the CLIC. For different
polarization configurations, we calculate the lower limits of the unparticle
energy scale Lambda_U for a discovery reach at the center of mass energies
sqrt(s)=0.5 TeV- 3 TeV. It is shown that, especially, for smaller values of the
mass dimension d, (1 <d <1.3), and for high energies and luminosities of the
collider these bounds are very significant. As a stringent limit, we find
Lambda_U>80 TeV for d<1.3 at sqrt(s)=3 TeV, and 1 ab^(-1) integrated luminosity
per year, which is comparable with the limits calculated from other low and
high energy physics implications.Comment: Table 1 and 2 have been combined as Table 1, references updated,
minor typos have been correcte
Constraints on Astro-unparticle Physics from SN 1987A
SN 1987A observations have been used to place constraints on the interactions
between standard model particles and unparticles. In this study we calculate
the energy loss from the supernovae core through scalar, pseudo scalar, vector,
pseudo vector unparticle emission from nuclear bremsstrahlung for degenerate
nuclear matter interacting through one pion exchange. In order to examine the
constraints on we considered the emission of scalar, pseudo
scalar, vector, pseudo vector and tensor through the pair annihilation process
. In addition we have re-examined other pair
annihilation processes. The most stringent bounds on the dimensionless coupling
constants for and are obtained from
nuclear bremsstrahlung process for the pseudo scalar and pseudo-vector
couplings and for
tensor interaction, the best limit on dimensionless coupling is obtained from
and we get .Comment: 12 pages, 2 postscript figure
Constraints from Solar and Reactor Neutrinos on Unparticle Long-Range Forces
We have investigated the impact of long-range forces induced by unparticle
operators of scalar, vector and tensor nature coupled to fermions in the
interpretation of solar neutrinos and KamLAND data. If the unparticle couplings
to the neutrinos are mildly non-universal, such long-range forces will not
factorize out in the neutrino flavour evolution. As a consequence large
deviations from the observed standard matter-induced oscillation pattern for
solar neutrinos would be generated. In this case, severe limits can be set on
the infrared fix point scale, Lambda_u, and the new physics scale, M, as a
function of the ultraviolet (d_UV) and anomalous (d) dimension of the
unparticle operator. For a scalar unparticle, for instance, assuming the
non-universality of the lepton couplings to unparticles to be of the order of a
few per mil we find that, for d_UV=3 and d=1.1, M is constrained to be M >
O(10^9) TeV (M > O(10^10) TeV) if Lambda_u= 1 TeV (10 TeV). For given values of
Lambda_u and d, the corresponding bounds on M for vector [tensor] unparticles
are approximately 100 [3/Sqrt(Lambda_u/TeV)] times those for the scalar case.
Conversely, these results can be translated into severe constraints on
universality violation of the fermion couplings to unparticle operators with
scales which can be accessible at future colliders.Comment: 13 pages, 3 figures. Minor changes due to precision in numerical
factors and correction in figure labels. References added. Conclusions remain
unchange
Upper limits on the Peccei-Quinn scale and on the reheating temperature in axino dark matter scenarios
Considering axino cold dark matter scenarios with a long-lived charged slepton, we study constraints on the Peccei–Quinn scale fa and on the reheating temperature TR imposed by the dark matter density and by big bang nucleosynthesis (BBN). For an axino mass compatible with large-scale structure, View the MathML source, temperatures above 109 GeV become viable for fa>3×1012 GeV. We calculate the slepton lifetime in hadronic axion models. With the dominant decay mode being two-loop suppressed, this lifetime can be sufficiently large to allow for primordial bound states leading to catalyzed BBN of lithium-6 and beryllium-9. This implies new upper limits on fa and on TR that depend on quantities which will be probed at the Large Hadron Collider