Search results for " Standard Model"
showing 10 items of 645 documents
Searching for a hidden sector in multiparticle production at LHC
2016
A hidden sector beyond the Standard Model can show up in multiparticle production altering inclusive correlations and factorial cumulants of multiplicity distributions. In this report such a study is advocated with a special emphasis on the searches at LHC.
D6-brane model building onZ2×Z6: MSSM-like and left–right symmetric models
2015
Abstract We perform a systematic search for globally defined MSSM-like and left–right symmetric models on D6-branes on the T 6 / ( Z 2 × Z 6 × Ω R ) orientifold with discrete torsion. Our search is exhaustive for models that are independent of the value of the one free complex structure modulus. Preliminary investigations suggest that there exists one prototype of visible sector for MSSM-like and another for left–right symmetric models with differences arising from various hidden sector completions to global models. For each prototype, we provide the full matter spectrum, as well as the Yukawa and other three-point couplings needed to render vector-like matter states massive. This provides …
Impeded Dark Matter
2016
We consider dark matter models in which the mass splitting between the dark matter particles and their annihilation products is tiny. Compared to the previously proposed Forbidden Dark Matter scenario, the mass splittings we consider are much smaller, and are allowed to be either positive or negative. To emphasize this modification, we dub our scenario "Impeded Dark Matter". We demonstrate that Impeded Dark Matter can be easily realized without requiring tuning of model parameters. For negative mass splitting, we demonstrate that the annihilation cross-section for Impeded Dark Matter depends linearly on the dark matter velocity or may even be kinematically forbidden, making this scenario al…
Unifying leptogenesis, dark matter and high-energy neutrinos with right-handed neutrino mixing via Higgs portal
2016
We revisit a model in which neutrino masses and mixing are described by a two right-handed (RH) neutrino seesaw scenario, implying a strictly hierarchical light neutrino spectrum. A third decoupled RH neutrino, $N_{\rm DM}$ with mass $M_{\rm DM}$, plays the role of cold dark matter (DM) and is produced by the mixing with a source RH neutrino, $N_{\rm S}$ with mass $M_{\rm S}$, induced by Higgs portal interactions. The same interactions are also responsible for $N_{\rm DM}$ decays. We discuss in detail the constraints coming from DM abundance and stability conditions, showing that in the hierarchical case ($M_{\rm DM} \gg M_{\rm S}$) there is an allowed window on $M_{\rm DM}$, which necessar…
Updated collider and direct detection constraints on Dark Matter models for the Galactic Center gamma-ray excess
2016
Utilizing an exhaustive set of simplified models, we revisit dark matter scenarios potentially capable of generating the observed Galactic Center gamma-ray excess, updating constraints from the LUX and PandaX-II experiments, as well as from the LHC and other colliders. We identify a variety of pseudoscalar mediated models that remain consistent with all constraints. In contrast, dark matter candidates which annihilate through a spin-1 mediator are ruled out by direct detection constraints unless the mass of the mediator is near an annihilation resonance, or the mediator has a purely vector coupling to the dark matter and a purely axial coupling to Standard Model fermions. All scenarios in w…
Looking at the axionic dark sector with ANITA
2020
The ANITA experiment has recently observed two anomalous events emerging from well below the horizon. Even though they are consistent with tau cascades, a high energy Standard Model or Beyond the Standard Model explanation is challenging and in tension with other experiments. We study under which conditions the reflection of generic radio pulses can reproduce these signals. We propose that these pulses can be resonantly produced in the ionosphere via axion-photon conversion. This naturally explains the direction and polarization of the events and avoids other experimental bounds.
On unification and nucleon decay in supersymmetric grand unified theories based on SU(5)
2006
9 pages, 4 figures.-- ISI Article Identifier: 000247170700016.-- ArXiv pre-print available at: http://arxiv.org/abs/hep-ph/0610034
Scalar contributions to b→c(u)τν transitions
2017
Abstract We perform a comprehensive analysis of scalar contributions in b → c τ ν transitions including the latest measurements of R ( D ( ⁎ ) ) , the q 2 differential distributions in B → D ( ⁎ ) τ ν , the τ polarization asymmetry for B → D ⁎ τ ν , and the bound derived from the total width of the B c meson. We find that scalar contributions with the simultaneous presence of both left- and right-handed couplings to quarks can explain the available data, specifically R ( D ( ⁎ ) ) together with the measured differential distributions. However, the constraints from the total B c width present a slight tension with the current data on B → D ⁎ τ ν in this scenario, preferring smaller values fo…
QCD and Strongly Coupled Gauge Theories: Challenges and Perspectives
2014
We dedicate this document to the memory of Mikhail Polikarpov, who passed away in July 2013. Misha worked with us for decades as a convener of the “Confinement” section of the Quark Confinement and Hadron Spectrum Series. He guided and expanded the scientific discussion of that topic, inspiring and under taking new research avenues. From its initial conception, he supported the enterprise of this document and organized Sect. 8, writing the part on confinement himself. He attracted the XIth Conference on Quark Confinement and the Hadron Spectrum to St. Petersburg (September 8-12, 2014; see http://phys.spbu.ru/confxi.html). His warm and kind personality, his high sense of humor, his ideas in …
Ricci-Based Gravity theories and their impact on Maxwell and nonlinear electromagnetic models
2019
Abstract We extend the correspondence between metric-affine Ricci-Based Gravity the- ories and General Relativity (GR) to the case in which the matter sector is represented by linear and nonlinear electromagnetic fields. This complements previous studies focused on fluids and scalar fields. We establish the general algorithm that relates the matter fields in the GR and RBG frames and consider some applications. In particular, we find that the so-called Eddington-inspired Born-Infeld gravity theory coupled to Maxwell electromag- netism is in direct correspondence with GR coupled to Born-Infeld electromagnetism. We comment on the potential phenomenological implications of this relation.