Standard Model Interactions Research Articles

Probing the scale of ALP interactions with Fermi blazars

Gamma-rays from cosmological sources contain information about gamma-ray interactions. Standard model and non-standard model photon interactions along the path between the source and the observer can lead to changes in the energy or state of the photons, which in turn alters the observed energy spectrum of the source. In general, these interactions are a function of photon energy as well as source distance. Here we show how existing high energy gamma-ray observations of blazars can be used to constrain the coupling of axion-like-particles (ALPs) to the photon. The same ALP-photon coupling that has been invoked to explain the observations of TeV blazars beyond their pair production horizon is shown to have a potential effect on the data set of Fermi blazars.

Modified Lennard-Jones model: virial coefficients to the 7th order.

The modified Lennard-Jones potential, which simplifies the numerical simulations and maintains the realistic behavior of its parent, is proposed to a role of the standard interaction model for both the experimental and theoretical studies. The virial coefficients of this model up to the seventh order have been calculated for the range of temperatures kT/ɛ = 0.3-70. In the computations, a technique has been used, that combines the quadrature integration and Mayer Sampling Monte Carlo method (MSMC). Unlike the original MSMC, this technique does not require the reference coefficients of another potential and can be used in a wide range of temperatures for various interaction models.

Light sterile neutrinos in particle physics: Experimental status

Abstract Most of the neutrino oscillation results can be explained by the three-neutrino paradigm. However several anomalies in short baseline oscillation data, corresponding to an L/E of about 1 m/MeV, could be interpreted by invoking a hypothetical fourth neutrino. This new state would be separated from the three standard neutrinos by a squared mass difference Δ m n e w 2 ∼ 0.1 – 1 eV 2 and would have mixing angles of sin 2 2 θ e e ≳ 0.01 and sin 2 2 θ μ e ≳ 0.001 , in the electron disappearance and appearance channels, respectively. This new neutrino, often called sterile, would not feel standard model interactions but mix with the others. Such a scenario calling for new physics beyond the standard model has to be either ruled out or confirmed with new data. After a brief review of the anomalous oscillation results we discuss the forthcoming laboratory experiments aiming to clarify the situation.

Higher dimensional operators and the LHC Higgs data: The role of modified kinematics

The inclusion of higher-dimensional gauge invariant operators induces new Lorentz structures in Higgs couplings with electroweak gauge boson pairs. This in principle affects the kinematics of Higgs production and decay, thereby modifying the efficiencies of the experimental cuts compared to what simulations based on the standard model interactions yield. Taking some sample cases, we perform a rigorous analysis of how the efficiencies differ for various strengths of the additional operator vis-a-vis the standard model interactions, scanning over the values of both of them. While the response to cuts can be markedly different in some regions, we find that the sensitivity to new operator structures is relatively limited, so long as we remain confined to the 2-sigma regions around the best fit signal strengths measured at the Large Hadron Collider. We also show modifications to certain kinematical distributions including the new operators in the diphoton final state.

Large neutrino magnetic dipole moments in MSSM extensions

An analysis of the Dirac neutrino magnetic moment with standard model interactions gives ${\ensuremath{\mu}}_{\ensuremath{\nu}}\ensuremath{\sim}3\ifmmode\times\else\texttimes\fi{}1{0}^{\ensuremath{-}19}{\ensuremath{\mu}}_{B}({m}_{\ensuremath{\nu}}/1\text{ }\text{ }\text{eV})$. The observation of a significantly larger magnetic moment will provide a clear signal of new physics beyond the standard model. The current experimental limits on the neutrino magnetic moments are orders of magnitude larger than the prediction with the standard model interactions and thus its test appears out of reach. Here we give an analysis of the Dirac neutrino magnetic moments within the framework of a minimal supersymmetric standard model extension with a vectorlike lepton generation. Specifically we compute the moments arising from the exchange of $W$ and the charged leptons in the loop, as well as from the exchange of charginos, charged sleptons and charged mirror sleptons. It is shown that the neutrino moment in this case can be several orders of magnitude larger than the one with standard model-like interactions, lying close to and below the current experimental upper limits and should be accessible in an improved future experiment. A correlated prediction of the heaviest neutrino lifetimes from radiative decays to the lighter neutrinos via exchange of charginos and sleptons in the loops is also made. The predicted lifetimes are several orders of magnitude smaller than the one with the standard model interactions and also lie close to the current experimental limits from analyses using the cosmic background neutrino data.

Discovery reach of CP violation in neutrino oscillation experiments with standard and non-standard interactions

Considering the value of mixing angle θ13 as obtained in recent Daya Bay and MINOS experiments we have explored the discovery reach of CP violation in the leptonic sector due to complex δ phase in neutrino oscillation experiments with superbeam. We have considered two experimental set-up corresponding to two baselines of 130 Km and 2300 Km respectively. Considering numerical simulation we have shown how the discovery reach of CP violation will change due to the presence of various non-standard interactions (NSIs). Although it is known that short baseline is better choice for CP violation study for Standard Model (SM) interactions of neutrinos with matter but in presence of NSI we find that sometimes better discovery reach is possible in relatively longer baselines.

Was Newton right? A search for non-Newtonian behavior of weak-field gravity

Empirical tests of Einstein's metric theory of gravitation, even in the non- relativistic, weak-field limit, could play an important role in judging theory-driven extensions of the current Standard Model of fundamental interactions. Guided by Galileo's work and his own experiments, Newton formulated a theory of gravity in which the force of attraction between two bodies is independent of composition and proportional to the inertia of each, thereby transparently satisfying Galileo's empirically informed conjecture regarding the Universality of Free Fall. Similarly, Einstein honored the manifest success of Newton's theory by assuring that the linearized equations of GTR matched the Newtonian formalism under classical conditions. Each of these steps, however, was explicitly an approximation raised to the status of principle. Perhaps, at some level, Newtonian gravity does not accurately describe the physical interaction between uncharged, unmagnetized, macroscopic bits of ordinary matter. What if Newton were wrong? Detecting any significant deviation from Newtonian behavior, no matter how small, could provide new insights and possibly reveal new physics. In the context of physics as an empirical science, for us this yet unanswered question constitutes sufficient motivation to attempt precision measurements of the kind described here. In this paper we report the current status of a project to search for violation of the Newtonian inverse square law of gravity.

Cyclotrons as Drivers for Precision Neutrino Measurements

As we enter the age of precision measurement in neutrino physics, improved flux sources are required. These must have a well defined flavor content with energies in ranges where backgrounds are low and cross-section knowledge is high. Very few sources of neutrinos can meet these requirements. However, pion/muon and isotope decay-at-rest sources qualify. The ideal drivers for decay-at-rest sources are cyclotron accelerators, which are compact and relatively inexpensive. This paper describes a scheme to produce decay-at-rest sources driven by such cyclotrons, developed within the DAEδALUS program. Examples of the value of the high precision beams for pursuing Beyond Standard Model interactions are reviewed. New results on a combined DAEδALUS—Hyper-K search for CP violation that achieve errors on the mixing matrix parameter of 4° to 12° are presented.

STATUS OF STANDARD MODEL CALCULATION OF LEPTON g - 2

The contributions from the standard model interactions to the anomalous magnetic moments of the two lightest charged leptons, the electron and the muon, are reviewed. Comparison with the very accurately measured experimental values is made, using the most recent high-precision determination of the fine structure constant.

Using effective operators to understand CoGeNT and CDMS-Si signals

Several direct detection experiments have reported positive signals consistent with a dark matter particle with a mass of approximately 7--9 GeV and a spin-independent scattering cross section of $2.5--4.8\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}41}\text{ }\text{ }{\mathrm{cm}}^{2}$. These results do not rise to the level of discovery, but assuming that they are due to dark matter, some questions about the underlying physics can already be addressed. In this paper, I apply the effective operator formalism for dark matter Standard Model interactions to the results of the CoGeNT and CDMS silicon target experiments. I demonstrate that only one set of flavor-blind effective operators between dark matter and quarks can be consistent with the reported results in all energy regimes of interest, namely thermal freeze-out, nuclear scattering, indirect detection, and TeV-scale colliders. This set of operators implies large couplings of dark matter with heavy quarks. The alternative implies either that the new physics has nontrivial flavor structure, that the effective formalism is not applicable and so contains new states in the spectrum accessible at the LHC, or has large annihilation channels (possibly via effective operators) into noncolored Standard Model particles.

Process interoperability in healthcare systems with dynamic semantic web services

Healthcare systems are very complex due to extreme heterogeneity in their data and processes. Researchers and practitioner need to make systems interoperable and integrate for the benefit of all the stakeholders including hospitals, clinicians, medical support staff, and patients. The broader goal of interoperability can only be achieved when standards are practiced.Two different healthcare systems can earn HL7 conformance and compliance but at the same time can be incompatible for interoperability because of varying implementation of HL7 interaction model. This is mainly because workflows in healthcare systems are very complex. Interoperability on one hand requires flexible mechanism for the mapping of business processes to a standard, HL7 in our example. On the other hand it requires deeper understanding of the standard interaction model and gaps created by their incompatible implementations. In this paper we propose a novel technique of dynamically creating semantic web services as overlay on top of the existing services. We used Web Service Modeling Framework as an underlying architecture for HL7 process artifacts implementation as semantic web services. These semantic services are mapped to our proposed interaction ontology. Integrated reasoning mechanism provides necessary execution semantics for more effective and seamless end-to-end communication.The prototype we tested on different processes from the laboratory domain at a local diagnostic laboratory with uninterrupted process flow. The scenario of Result Query Placer interaction flow and its associated process artifacts are executed for the proof of concept.The proposed solution complements the existing data interoperability in HL7 and leads to semantic process interoperability. The achievement of semantic interoperability results in timely delivery of healthcare services to patients saving precious lives.

Excited neutrino production by ultrahigh energy neutrinos traversing the Earth

We focus on the production of excited neutrinos by ultra high energy (UHE, ${E}_{\ensuremath{\nu}}>{10}^{4}\text{ }\text{ }\mathrm{GeV}$) neutrinos traversing the Earth. The surviving neutrino fluxes are calculated using the complete system of transport equations for ordinary neutrinos and their excited states, and we compare these results with the obtained using only Standard Model (SM) interactions. We extend the analysis by including the neutral current (NC) and decay regeneration effects, and computing the surviving flux for different values of $f/\ensuremath{\Lambda}$, where $\ensuremath{\Lambda}$ is the compositeness scale and $f$ a coupling factor representing non-perturbative physics. Finally, we analyze the possibilities of detecting such fluxes in a neutrino telescope such as IceCube showing the allowed regions in the $({m}^{*},f/\ensuremath{\Lambda})$ plane for two possible initial fluxes. We have considered the IC80 configuration of IceCube for an operation time of ten years.

On Lung Function and Interactions Using Genome-Wide Data

On Lung Function and Interactions Using Genome-Wide Data

Effect of transition magnetic moments on collective supernova neutrino oscillations

We study the effect of Majorana transition magnetic moments on the flavor evolution of neutrinos and antineutrinos inside the core of Type-II supernova explosions. We find non-trivial collective oscillation effects relating neutrinos and antineutrinos of different flavors, even if one restricts the discussion to Majorana transition electromagnetic moment values that are not much larger than those expected from standard model interactions and nonzero neutrino Majorana masses. This appears to be, to the best of our knowledge, the only potentially observable phenomenon sensitive to such small values of Majorana transition magnetic moments. We briefly comment on the effect of Dirac transition magnetic moments and on the consequences of our results for future observations of the flux of neutrinos of different flavors from a nearby supernova explosion.

Precision mass measurements for nuclear astro- and neutrino physics

Nuclear masses are indispensable ingredients in numerous physics applications ranging from nuclear structure physics, where, e.g., the shell closures and nucleon correlation energies can be studied by accurate mass measurements, via the nuclear astrophysics, where the masses of nuclei far from the valley of β-stability determine the pathways of, e.g., rp-and r-processes of nucleosynthesis in stars, to tests of the standard model and fundamental interactions, where, e.g., the very-accurate masses of parent and superallowed β-decay daughter nuclei serve as one of inputs for the checking of the unitarity of the CKM quark-mixing matrix. In this review we focus on recent direct mass measurements conducted with storage rings and Penning trap mass spectrometry. Although these measurements have a broad impact, we restrict our discussion on two topics, namely nuclear astrophysics and neutrino physics.

Quartet condensation and isovector pairing correlations inN=Znuclei

We propose a simple quartet condensation model (QCM) which describes with very high accuracy the isovector pairing correlations in self-conjugate nuclei. The quartets have an $\ensuremath{\alpha}$-like structure and are formed by collective isovector pairs. The accuracy of the QCM is tested for $N=Z$ nuclei for which exact shell model diagonalizations can be performed. The calculations are done with two isovector pairing forces, one extracted from standard shell model interactions and the other of seniority type, acting, respectively, upon spherical and axially deformed single-particle states. It is shown that for all calculated nuclei the QCM gives very accurate values for the pairing correlations energies, with errors which do not exceed 1$%$. These results show clearly that the correlations induced by the isovector pairing in self-conjugate nuclei are of quartet type and also indicate that QCM is the proper tool to calculate the isovector proton-neutron correlations in mean field pairing models.

Global constraints on effective dark matter interactions: relic density, direct detection, indirect detection, and collider

An effective interaction approach is used to describe the interactions between the spin 0 or spin 1/2 dark matter particle and the degrees of freedom of the standard model. This approach is applicable to those models in which the dark matterparticles do not experience the standard-model interactions, e.g., hidden-sector models. We explore the effects of these effective interaction operators on (i) dark matter relic density, (ii) spin-independent and spin-dependent dark matter-nucleon scattering cross sections, (iii) cosmic antiproton and gamma ray fluxes from the galactic halo due to dark matter annihilation, and (iv) monojet and monophoton production plus missing energy at the Tevatron and the Large Hadron Collider (LHC). We combine the experimental data of relic density from WMAP7, spin-independent cross section from XENON100, spin-dependent cross section from XENON10, ZEPLIN-III, and SIMPLE, cosmic antiproton flux from PAMELA, cosmic gamma-ray flux from Fermi-LAT, and the monojet and monophoton data from the Tevatron and the LHC, to put the most comprehensive limits on each effective operator.

Missing energy signatures of dark matter at the LHC

We use ATLAS and CMS searches in the monojet $+$ missing energy and monophoton $+$ missing energy final state to set limits on the couplings of dark matter to quarks and gluons. Working in an effective field theory framework we compare several existing monojet analyses and find that searches with high ${p}_{T}$ cuts are more sensitive to dark matter. We constrain the suppression scale of the effective dark matter--standard model interactions and convert these limits into bounds on the cross sections relevant to direct and indirect detection. We find that, for certain types of operators, in particular, spin-independent dark matter--gluon couplings and spin-dependent dark matter--quark couplings, LHC constraints from the monojet channel are competitive with, or superior to, limits from direct searches up to dark matter masses of order 1 TeV. Comparing to indirect searches, we exclude, at 90% C.L., dark matter annihilating to quarks with the annihilation cross section of a thermal relic for masses below $\ensuremath{\sim}15--70\text{ }\text{ }\mathrm{GeV}$, depending on the Lorentz structure of the effective couplings. Monophoton limits are somewhat weaker than monojet bounds but still provide an important cross check in the case of a discovery in monojets. We also discuss the possibility that dark matter--standard model interactions at LHC energies cannot be described by effective operators, in which case we find that constraints can become either significantly stronger, or considerably weaker, depending on the mass and width of the intermediate particle. Further, we discuss the special case of dark matter coupling to the Higgs boson, and we show that searches for invisible Higgs decays would provide superior sensitivity, particularly for a light Higgs mass and light dark matter.

Cosmological limits on hidden sector dark matter

We explore the model-independent constraints from cosmology on a dark-matter particle with no prominent standard model interactions that interacts and thermalizes with other particles in a hidden sector. Without specifying detailed hidden-sector particle physics, we characterize the relevant physics by the annihilation cross section, mass, and temperature ratio of the hidden to visible sectors. While encompassing the standard cold WIMP scenario, we do not require the freeze-out process to be nonrelativistic. Rather, freeze-out may also occur when dark matter particles are semirelativistic or relativistic. We solve the Boltzmann equation to find the conditions that hidden-sector dark matter accounts for the observed dark-matter density, satisfies the Tremaine-Gunn bound on dark-matter phase space density, and has a free-streaming length consistent with cosmological constraints on the matter power spectrum. We show that for masses <1.5 keV no region of parameter space satisfies all these constraints. This is a gravitationally-mediated lower bound on the dark-matter mass for any model in which the primary component of dark matter once had efficient interactions -- even if it has never been in equilibrium with the standard model.

Mixed states from anomalies

There are several instances where quantum anomalies of continuous and discrete classical symmetries play an important role in fundamental physics. Examples come from chiral anomalies in the Standard Model of fundamental interactions and gravitational anomalies in string theories. Their generic origin is the fact that classical symmetries may not preserve the domains of quantum operators like the Hamiltonian. In this work, we show by simple examples that anomalous symmetries can often be implemented at the expense of working with mixed states having nonzero entropies. In particular there is the result on color breaking by non-abelian magnetic monopoles. This anomaly can be rectified by using impure states. We also argue that non-abelian groups of twisted bundles are always anomalous for pure states sharpening an earlier argument of Sorkin and Balachandran [A. P. Balachandran, G. Marmo, B. S. Skagerstam, and A. Stern, Classical Topology and Quantum States (World Scientific, Singapore, 1991).]. This is the case of mapping class groups of geons [A. P. Balachandran, G. Marmo, B. S. Skagerstam, and A. Stern, Classical Topology and Quantum States (World Scientific, Singapore, 1991).] indicating that large diffeos are anomalous for pure states in the presence of geons. Nevertheless diffeo invariance may be restored by using impure states. This work concludes with examples of these ideas drawn from molecular physics. The above approach using impure states is entirely equivalent to restricting all states to the algebra of observables invariant under the anomalous symmetries. For anomalous gauge groups such as color, this would mean that we work with observables singlet under global gauge transformations. For color, this will mean that we work with color singlets, a reasonable constraint.