375 research outputs found
Non-renormalizable Yukawa Interactions and Higgs Physics
We explore a scenario in the Standard Model in which dimension four Yukawa
couplings are either forbidden by a symmetry, or happen to be very tiny, and
the Yukawa interactions are dominated by effective dimension six interactions.
In this case, the Higgs interactions to the fermions are enhanced in a large
way, whereas its interaction with the gauge bosons remains the same as in the
Standard Model. In hadron colliders, Higgs boson production via gluon gluon
fusion increases by a factor of nine. Higgs decay widths to fermion
anti-fermion pairs also increase by the same factor, whereas the decay widths
to photon photon and gamma Z are reduced. Current Tevatron exclusion range for
the Higgs mass increases to ~ 142-200 GeV in our scenario, and new physics must
appear at a scale below a TeV.Comment: 5 pages, 4 figure
Quark lepton unification in higher dimensions
The idea of unifying quarks and leptons in a gauge symmetry is very
appealing. However, such an unification gives rise to leptoquark type gauge
bosons for which current collider limits push their masses well beyond the TeV
scale. We present a model in the framework of extra dimensions which breaks
such quark-lepton unification symmetry via compactification at the TeV scale.
These color triplet leptoquark gauge bosons, as well as the new quarks present
in the model, can be produced at the LHC with distinctive final state
signatures. These final state signals include high p_T multi-jets and
multi-leptons with missing energy, monojets with missing energy, as well as the
heavy charged particles passing through the detectors, which we also discuss
briefly. The model also has a neutral Standard Model singlet heavy lepton which
is stable, and can be a possible candidate for the dark matter.Comment: 28 pages, 5 eps figure
Neutrino Masses from Fine Tuning
We present a new approach for generating tiny neutrino masses. The Dirac
neutrino mass matrix gets contributions from two new Higgs doublets with their
vevs at the electroweak (EW) scale. Neutrino masses are tiny not because of
tiny Yukawa couplings, or very heavy () right handed
neutrinos. They are tiny because of a cancelation in the Dirac neutrino mass
matrix (fine tuning). After fine tuning to make the Dirac neutrino mass matrix
at the GeV scale, light neutrino masses are obtained in the correct
scale via the see-saw mechanism with the right handed neutrino at the EW scale.
The proposal links neutrino physics to collider physics. The Higgs search
strategy is completely altered. For a wide range of Higgs masses, the Standard
Model Higgs decays dominantly to mode giving rise to the final
state , or . This can be
tested at the LHC, and possibly at the Tevatron.Comment: 12 pages, 4 figures and 3 table
The Impact of a 4th Generation on Mixing and CP Violation in the Charm System
We study D0-D0 mixing in the presence of a fourth generation of quarks. In
particular, we calculate the size of the allowed CP violation which is found at
the observable level well beyond anything possible with CKM dynamics. We
calculate the semileptonic asymmetry a_SL and the mixing induced CP asymmetry
eta_fS_f which are correlated with each other. We also investigate the
correlation of eta_fS_f with a number of prominent observables in other mesonic
systems like epsilon'/epsilon, Br(K_L -> pi0 nu nu), Br(K+ -> pi+ nu nu),
Br(B_s ->mu+ mu-), Br(B_d -> mu+ mu-) and finally S_psi phi in the B_s system.
We identify a clear pattern of flavour and CP violation predicted by the SM4
model: While simultaneous large 4G effects in the K and D systems are possible,
accompanying large NP effects in the B_d system are disfavoured. However this
behaviour is not as pronounced as found for the LHT and RSc models. In contrast
to this, sizeable CP violating effects in the B_s system are possible unless
extreme effects in eta_fS_f are found, and Br(B_s ->mu+ mu-) can be strongly
enhanced regardless of the situation in the D system. We find that, on the
other hand, S_psi phi > 0.2 combined with the measured epsilon'/epsilon
significantly diminishes 4G effects within the D system.Comment: 22 pages, 23 figures, v2 (references added
Four Generations: SUSY and SUSY Breaking
We revisit four generations within the context of supersymmetry. We compute
the perturbativity limits for the fourth generation Yukawa couplings and show
that if the masses of the fourth generation lie within reasonable limits of
their present experimental lower bounds, it is possible to have perturbativity
only up to scales around 1000 TeV. Such low scales are ideally suited to
incorporate gauge mediated supersymmetry breaking, where the mediation scale
can be as low as 10-20 TeV. The minimal messenger model, however, is highly
constrained. While lack of electroweak symmetry breaking rules out a large part
of the parameter space, a small region exists, where the fourth generation stau
is tachyonic. General gauge mediation with its broader set of boundary
conditions is better suited to accommodate the fourth generation.Comment: 27 pages, 5 figure
Defending the genome from the enemy within:mechanisms of retrotransposon suppression in the mouse germline
The viability of any species requires that the genome is kept stable as it is transmitted from generation to generation by the germ cells. One of the challenges to transgenerational genome stability is the potential mutagenic activity of transposable genetic elements, particularly retrotransposons. There are many different types of retrotransposon in mammalian genomes, and these target different points in germline development to amplify and integrate into new genomic locations. Germ cells, and their pluripotent developmental precursors, have evolved a variety of genome defence mechanisms that suppress retrotransposon activity and maintain genome stability across the generations. Here, we review recent advances in understanding how retrotransposon activity is suppressed in the mammalian germline, how genes involved in germline genome defence mechanisms are regulated, and the consequences of mutating these genome defence genes for the developing germline
Problematic mobile phone use and smartphone addiction across generations: the roles of psychopathological symptoms and smartphone use
Contemporary technological advances have led to a significant increase in using mobile technologies. Recent research has pointed to potential problems as a consequence of mobile overuse, including addiction, financial problems, dangerous use (i.e. whilst driving) and prohibited use (i.e. use in forbidden areas). The aim of this study is to extend previous findings regarding the predictive power of psychopathological symptoms (depression, anxiety and stress), mobile phone use (i.e. calls, SMS, time spent on the phone, as well as the engagement in specific smartphone activities) across Generations X and Y on problematic mobile phone use in a sample of 273 adults. Findings revealed prohibited use and dependence were predicted by calls/day, time on the phone and using social media. Only for dependent mobile phone use (rather than prohibited), stress appeared as significant. Using social media and anxiety significantly predicted belonging to Generation Y, with calls per day predicted belonging to Generation X. This finding suggests Generation Y are more likely to use asynchronous social media-based communication, whereas Generation X engage more in synchronous communication. The findings have implications for prevention and awareness-raising efforts of possibly problematic mobile phone use for educators, parents and individuals, particularly including dependence and prohibited use
Perspectives for next generation lithium-ion battery cathode materials
Transitioning to electrified transport requires improvements in sustainability, energy density, power density, lifetime, and approved the cost of lithium-ion batteries, with significant opportunities remaining in the development of next-generation cathodes. This presents a highly complex, multiparameter optimization challenge, where developments in cathode chemical design and discovery, theoretical and experimental understanding, structural and morphological control, synthetic approaches, and cost reduction strategies can deliver performance enhancements required in the near- and longer-term. This multifaceted challenge requires an interdisciplinary approach to solve, which has seen the establishment of numerous academic and industrial consortia around the world to focus on cathode development. One such example is the Next Generation Lithium-ion Cathode Materials project, FutureCat, established by the UK’s Faraday Institution for electrochemical energy storage research in 2019, aimed at developing our understanding of existing and newly discovered cathode chemistries. Here, we present our perspective on persistent fundamental challenges, including protective coatings and additives to extend lifetime and improve interfacial ion transport, the design of existing and the discovery of new cathode materials where cation and cation-plus-anion redox-activity can be exploited to increase energy density, the application of earth-abundant elements that could ultimately reduce costs, and the delivery of new electrode topologies resistant to fracture which can extend battery lifetime.</jats:p
Perspectives for next generation lithium-ion battery cathode materials
Transitioning to electrified transport requires improvements in sustainability, energy density, power density, lifetime, and approved the cost of lithium-ion batteries, with significant opportunities remaining in the development of next-generation cathodes. This presents a highly complex, multiparameter optimization challenge, where developments in cathode chemical design and discovery, theoretical and experimental understanding, structural and morphological control, synthetic approaches, and cost reduction strategies can deliver performance enhancements required in the near- and longer-term. This multifaceted challenge requires an interdisciplinary approach to solve, which has seen the establishment of numerous academic and industrial consortia around the world to focus on cathode development. One such example is the Next Generation Lithium-ion Cathode Materials project, FutureCat, established by the UK’s Faraday Institution for electrochemical energy storage research in 2019, aimed at developing our understanding of existing and newly discovered cathode chemistries. Here, we present our perspective on persistent fundamental challenges, including protective coatings and additives to extend lifetime and improve interfacial ion transport, the design of existing and the discovery of new cathode materials where cation and cation-plus-anion redox-activity can be exploited to increase energy density, the application of earth-abundant elements that could ultimately reduce costs, and the delivery of new electrode topologies resistant to fracture which can extend battery lifetime
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