Indirect Constraints Research Articles

Effects of family nonuniversalZ′boson on leptonic decays of Higgs and weak bosons

Though not completely a surprise according to the standard model and existing indirect constraints, the Higgs-like particle, h, of mass around 125 GeV recently observed at the LHC may offer an additional window to physics beyond the standard model. In particular, its decay pattern can be modified by the existence of new particles. One of the popular scenarios involves a Z' boson associated with an extra Abelian gauge group. In this study, we explore the potential effects of such a boson with family-nonuniversal couplings on the leptonic decays of h, both flavor-conserving and flavor-changing. For current constraints, we take into account leptonic decays at the Z pole, LEP II scattering data, limits on various flavor-changing lepton transitions, and lepton magnetic dipole moments. Adopting a model-independent approach and assuming that the Z' has negligible mixing with the Z boson, we find that present data allow the Z' effects to reach a few percent or higher on h decays into a pair of leptons. Future measurements on h at the LHC or a linear collider can therefore detect the Z' contributions or impose further constraints on its couplings. We also consider Z'-mediated four-lepton decays of the Z and W bosons.

Electroweak baryogenesis and the Fermi gamma-ray line

Many particle physics models attempt to explain the 130 GeV gamma-ray feature that the Fermi large area telescope observes in the Galactic center. Neutralino dark matter in nonminimal supersymmetric models, such as the next-to-minimal supersymmetric standard Model (NMSSM), is an especially well-motivated theoretical setup that can explain the line. We explore the possibility that regions of the NMSSM consistent with the 130 GeV line can also produce the observed baryon asymmetry of the universe via electroweak baryogenesis. We find that such regions can, in fact, accommodate a strongly first-order electroweak phase transition (due to the singlet contribution to the effective potential), while also avoiding a light stop and producing a Standard Model (SM)-like Higgs in the observed mass range. Simultaneously, $CP$ violation from a complex phase in the wino-Higgsino sector can account for the observed baryon asymmetry through resonant sources at the electroweak phase transition, while satisfying current constraints from dark matter, collider, and electric dipole moment experiments. This result is possible by virtue of a relatively light pseudoscalar Higgs sector with a small degree of mixing, which yields efficient $s$-channel resonant neutralino annihilation consistent with indirect detection constraints, and of the moderate values of $\ensuremath{\mu}$ required to obtain a binolike lightest supersymmetric particle consistent with the line. The wino mass is essentially a free parameter that one can tune to satisfy electroweak baryogenesis. Thus, the NMSSM framework can potentially explain the origins of both baryonic and dark matter components in the Universe. The tightness of the constraints we impose on this scenario makes it extraordinarily predictive and conclusively testable in the near future by modest improvements in electric dipole moment and dark matter search experiments.

Electroweak theory and global fit

We perform the fit of electroweak precision observables within the Standard Model with a 126 GeV Higgs boson, compare the results with the theoretical predictions and discuss the impact of recent experimental and theoretical improvements. We introduce New Physics contributions in a model-independent way and fit for the S , T and U parameters and for a modified Higgs coupling to vector bosons. We point out that compos- ite Higgs models are very strongly constrained. Finally, we compute the bounds on dimension-six operators relevant for the electroweak fit. Electroweak Precision Observables (EWPO) have played a key role in constraining New Physics (NP) for the past twenty years (1-11). The most striking exam- ples of the power of these indirect constraints are the pre- diction of the top and Higgs masses. The experimen- tal situation improved dramatically in the past year, with the precise measurement of the Higgs mass at the LHC (12, 13). In addition, the information on other key Stan- dard Model (SM) parameters such as the top and W boson masses has increased considerably, leading altogether to a sizable progress in the electroweak (EW) fit. It is therefore phenomenologically relevant to reassess the constraining power of the EW fit in the light of these recent experimen- tal improvements. To this aim, we perform the EW fit in the SM and update the constraints on oblique NP. On the theory side, the full two-loop fermionic EW contributions to the R 0 observable have been recently numerically cal- culated in ref. (14). The implementation of this result in the global fit has a large impact but represents a nontriv- ial problem, as we illustrate in detail below. A very in- teresting question that can be tackled with present data is whether the Higgs boson is elementary or composite. Us- ing a general e ective Lagrangian for Higgs boson inter- actions (15-18), we analyze the constraints on the Higgs coupling to vector bosons, and find out that this coupling can be determined from the fit with an uncertainty of 5% at 95% probability, while much larger departures from the SM value are expected in generic composite Higgs mod- els. Thus, the EW fit points to an elementary Higgs or to composite Higgs models in which additional contributions are present to restore the agreement with EWPO. Finally, we consider the most general e ective Lagrangian relevant

The Composition Forecasting Research for Cupola Melting Process

This paper summarizes components and phases involved in the cupola melting process, then brings out a composition forecasting model based on the minimum Gibbs energy principle and the equilibria calculation algorithms of multiphase and multicomponent. Besides, the relationship between the melting parameters and the composition of molten iron is set up by using BP neural network based on the idea of indirect constraints. Finally, the paper probes the feasibility of the composition forecasting model with two examples. The application result shows that the prediction with this method can achieve strong practicability and popularization value.

Status of the inert doublet model and the role of multileptons at the LHC

A possible feature of the inert doublet model (IDM) is to provide a dark matter candidate together with an alteration of both direct and indirect collider constraints that allow for a heavy Higgs boson. We study the IDM in light of recent results from Higgs searches at the Large Hadron Collider (LHC) in combination with dark matter direct detection limits from the XENON experiment. We ask under what conditions the IDM can still accommodate a heavy Higgs boson. We find that IDM scenarios with a Higgs boson in the mass range 160-600 GeV are ruled out only when all experimental constraints are combined. For models explaining only a fraction of the dark matter the limits are weakened, and IDMs with a heavy Higgs are allowed. We discuss the prospects for future detection of such IDM scenarios in the four-lepton plus missing energy channel at the LHC. This signal can show up in the first year of running at \sqrt{s} = 14 TeV, and we present detector-level studies for a few benchmark models.

Neutrinos from off-shell final states and the indirect detection of dark matter

We revisit the annihilation of dark matter to neutrinos in the Sun near the ${W}^{+}{W}^{\ensuremath{-}}$ and $t\overline{t}$ kinematic thresholds. We investigate the potential importance of annihilation to $W{W}^{*}$ in a minimal dark matter model in which a Majorana singlet is mixed with a vectorlike electroweak doublet, but many results generalize to other models of weakly interacting dark matter. We reevaluate the indirect detection constraints on this model and find that, once all annihilation channels are properly taken into account, the most stringent constraints on spin-dependent scattering for dark matter mass $60\text{ }\text{ }\mathrm{GeV}\ensuremath{\lesssim}{m}_{\ensuremath{\chi}}\ensuremath{\lesssim}{m}_{t}$ are derived from the results of the Super-Kamiokande experiment. Moreover, we establish the model-independent statement that Majorana dark matter whose thermal relic abundance and neutrino signals are both controlled by annihilation via an $s$-channel $Z$ boson is excluded for $70\text{ }\text{ }\mathrm{GeV}\ensuremath{\lesssim}{m}_{\ensuremath{\chi}}\ensuremath{\lesssim}{m}_{W}$. In some models, annihilation to $t{t}^{*}$ can affect indirect detection, notably by competing with annihilation to gauge boson final states and thereby weakening neutrino signals. However, in the minimal model, this final state is largely negligible, only allowing dark matter with mass a few GeV below the top quark mass to evade exclusion.

The empirical case for 10-GeV dark matter

Abstract In this article, I summarize and discuss the body of evidence which has accumulated in favor of dark matter in the form of approximately 10-GeV particles. This evidence includes the spectrum and angular distribution of γ-rays from the Galactic Center, the synchrotron emission from the Milky Way’s radio filaments, the diffuse synchrotron emission from the Inner Galaxy (the “WMAP Haze”) and low-energy signals from the direct detection experiments DAMA/LIBRA, CoGeNT and CRESST-II. This collection of observations can be explained by a relatively light dark matter particle with an annihilation cross section consistent with that predicted for a simple thermal relic ( σv ∼ 10 −26 cm 3 /s) and with a distribution in the halo of the Milky Way consistent with that predicted from simulations. Astrophysical explanations for the γ-ray and synchrotron signals, in contrast, have not been successful in accommodating these observations. Similarly, the phase of the annual modulation observed by DAMA/LIBRA (and now supported by CoGeNT) is inconsistent with all known or postulated modulating backgrounds, but are in good agreement with expectations for dark matter scattering. This scenario is consistent with all existing indirect and collider constraints, as well as the constraints placed by CDMS. Consistency with xenon-based experiments can be achieved if the response of liquid xenon to very low-energy nuclear recoils is somewhat suppressed relative to previous evaluations, or if the dark matter possesses different couplings to protons and neutrons.

On the relative contribution of high-redshift galaxies and active galactic nuclei to reionization

In this paper we discuss the contribution of different astrophysical sources to the ionization of neutral hydrogen at different redshifts. We critically revise the arguments in favour/against a substantial contribution of Active Galactic Nuclei (AGNs) and/or Lyman Break Galaxies (LBGs) to the reionization of the Universe at z>5. We consider extrapolations of the high-z QSO and LBG luminosity functions and their redshift evolution as well as indirect constraints on the space density of lower luminosity Active Galactic Nuclei based on the galaxy stellar mass function. Since the hypothesis of a reionization due to LBGs alone requires a significant contribution of faint dwarf galaxies and a LyC photon escape fraction (f_esc) of the order of ~20%, in tension with present observational constraints, we examine under which hypothesis AGNs and LBGs may provide a combined relevant contribution to the reionization. We show that a relatively steep faint-end of the AGN luminosity function, consistent with present constraints, provides a relevant (although sub-dominant) contribution, thus allowing us to recover the required ionizing photon rates with f_esc~5% up to z~7. At higher redshifts, we test the case for a luminosity-dependent f_esc scenario and we conclude that, if the observed LBGs are indeed characterized by very low f_esc, values of the order of f_esc~70% are needed for objects below our detection threshold, for this galaxy population to provide a substantial contribution to reionization. Clearly, the study of the properties of faint sources (both AGNs and LBGs) is crucial.

Hiding a heavy Higgs boson at the 7 TeV LHC

Abstract A heavy Standard Model Higgs boson is not only disfavored by electroweak precision observables but is also excluded by direct searches at the 7 TeV LHC for a wide range of masses. Here, we examine scenarios where a heavy Higgs boson can be made consistent with both the indirect constraints and the direct null searches by adding only one new particle beyond the Standard Model. This new particle should be a weak multiplet in order to have additional contributions to the oblique parameters. If it is a color singlet, we find that a heavy Higgs with an intermediate mass of 200–300 GeV can decay into the new states, suppressing the branching ratios for the standard model modes, and thus hiding a heavy Higgs at the LHC. If the new particle is also charged under QCD, the Higgs production cross section from gluon fusion can be reduced significantly due to the new colored particle one-loop contribution. Current collider constraints on the new particles allow for viable parameter space to exist in order to hide a heavy Higgs boson. We categorize the general signatures of these new particles, identify favored regions of their parameter space and point out that discovering or excluding them at the LHC can provide important in- direct information for a heavy Higgs. Finally, for a very heavy Higgs boson, beyond the search limit at the 7 TeV LHC, we discuss three additional scenarios where models would be consistent with electroweak precision tests: including an additional vector-like fermion mixing with the top quark, adding another U(1) gauge boson and modifying triple-gauge boson couplings.

BBN with electron-sterile neutrino oscillations — the finest leptometer

A relic lepton asymmetry orders of magnitude bigger than the baryon one may hide in the relic neutrino background. No direct theoretical or experimental limitations on its magnitude and sign are known. Only indirect cosmological constraints exist ranging from |L| < 0.01 to L < 10. Here we discuss a Big Bang Nucleosynthesis (BBN) model with late electron-sterile neutrino oscillations. The influence of L on neutrino oscillations and on nucleons freezing in the pre-BBN epoch is numerically analyzed in the full range of the oscillation parameters of the model and for |L| ⩾ 10−10. The asymmetry-oscillations interplay is studied in detail and the behavior of L for different oscillation parameters is found. L effect on the primordially produced 4He is precisely studied. It is shown that this BBN model is a fine leptometer, capable of feeling extremely small relic lepton asymmetry — |L| > 10−8. The case of oscillations generated asymmetry by late electron-sterile oscillations and its effect on the primordial 4He is also briefly discussed. The instability region of the asymmetry growth is obtained.

Spontaneous mirror parity violation, common origin of matter and dark matter, and the LHC signatures

Existence of a mirror world in the Universe is a fundamental way to restore the observed parity violation in weak interactions and provides the lightest mirror nucleon as a unique GeV-scale dark matter particle candidate. The visible and mirror worlds share the same spacetime of the Universe and are connected by a unique space-inversion symmetry---the mirror parity ($P$). We conjecture that the mirror parity is respected by the fundamental interaction Lagrangian, and study its spontaneous breaking from minimizing the Higgs vacuum potential. The domain-wall problem is resolved by a unique soft-breaking linear term from the $P$-odd weak-singlet Higgs field. We also derive a constraint from big-bang nucleosynthesis. We then analyze the neutrino seesaw for both visible and mirror worlds, and demonstrate that the desired amounts of visible matter and mirror dark matter in the Universe arise from a common origin of $CP$ violation in the neutrino sector via leptogenesis. We derive the Higgs mass spectrum and Higgs couplings with gauge bosons and fermions. We show their consistency with the direct Higgs searches and the indirect precision constraints. We further study the distinctive signatures of the predicted nonstandard Higgs bosons at the LHC. Finally, we analyze the direct detections of GeV-scale mirror dark matter by the TEXONO and CDEX experiments.

Flavour-changing decays of a 125 GeV Higgs-like particle

The ATLAS and CMS experiments at the LHC have reported the observation of a possible excess of events corresponding to a new particle h with mass ∼125 GeV that might be the long-sought Higgs boson, or something else. Decyphering the nature of this possible signal will require constraining the couplings of the h and measuring them as accurately as possible. Here we analyze the indirect constraints on flavour-changing h decays that are provided by limits on low-energy flavour-changing interactions. We find that indirect limits in the quark sector impose such strong constraints that flavour-changing h decays to quark–antiquark pairs are unlikely to be observable at the LHC. On the other hand, the upper limits on lepton-flavour-changing decays are weaker, and the experimental signatures less challenging. In particular, we find that either B(h→τμ¯+μ¯τ) or B(h→τe¯+e¯τ) could be O(10)%, i.e., comparable to B(h→τ+τ−) and potentially observable at the LHC.

Constraining the dipole moments of the top quark

We investigate the direct and indirect bounds on dipole operators involving the top quark. A careful analysis shows that the experimental upper limit on the neutron electric dipole moment strongly constrains the chromo-electric dipole of the top. We improve previous bounds by 2 orders of magnitude. This has significant implications for new physics models and it also means that $CP$ violation in top pair production mediated by dipole operators will not be accessible at the LHC. The $CP$ conserving chromo-magnetic dipole moments are constrained by recent measurements of the $t\overline{t}$ spectrum by the ATLAS collaboration. We also update the indirect constraints on electric and magnetic dipole moments from radiative $b\ensuremath{\rightarrow}s$ transitions, finding that they can be considerably larger than their colored counterparts.

SUSY, the Third Generation and the LHC

We develop a bottom-up approach to studying SUSY with light stops and sbottoms, but with other squarks and sleptons heavy and beyond reach of the LHC. We discuss the range of squark, gaugino and Higgsino masses for which the electroweak scale is radiatively stable over the "little hierarchy" below ~ 10 TeV. We review and expand on indirect constraints on this scenario, in particular from flavor and CP tests. We emphasize that in this context, R-parity violation is very well motivated. The phenomenological differences between Majorana and Dirac gauginos are also discussed. Finally, we focus on the light subsystem of stops, sbottom and neutralino with R-parity, in order to probe the current collider bounds. We find that 1/fb LHC bounds are mild and large parts of the motivated parameter space remain open, while the 10/fb data can be much more decisive.

The complementarity of SuperBwith the LHC

The complementarity between results anticipated from SuperB with those from the LHC experiments is discussed here. SuperB can contribute to searches for new physics using indirect constraints via precision tests of the standard model. In addition to the indirect constraints, there are a number of direct searches that can be performed at low energy. There is a well motivated programme of measurements to make at SuperB, the results of which will add to our understanding of possible scenarios of physics beyond the standard model.

The effects of direct and indirect constraints on biological communities

Human activities are expected to result in a diversity of directional or stochastic constraints that affect species either directly or by indirectly impacting their resources. However, there is no theoretical framework to predict the complex and various effects of these constraints on ecological communities. We developed a dynamic model that mimics the use of different resource types by a community of competing species. We investigated the effects of different environmental constraints (affecting either directly the growth rate of species or having indirect effects on their resources) on several biodiversity indicators. Our results indicate that (i) in realistic community models (assuming uneven resource requirements among species) the effects of perturbations are strongly buffered compared to neutral models; (ii) the species richness of communities can be maximized for intermediate levels of direct constraints (unimodal response), even in the absence of trade-off between competitive ability and tolerance to constraints; (iii) no such unimodal response occurs with indirect constraints; (iv) an increase in the environmental (e.g., climatic) variance may have different effects on community biomass and species richness.

Goldstone fermion dark matter

We propose that the fermionic superpartner of a weak-scale Goldstone boson can be a natural WIMP candidate. The p-wave annihilation of this ‘Goldstone fermion’ into pairs of Goldstone bosons automatically generates the correct relic abundance, whereas the XENON100 direct detection bounds are evaded due to suppressed couplings to the Standard Model. Further, it is able to avoid indirect detection constraints because the relevant s-wave annihilations are small. The interactions of the Goldstone supermultiplet can induce non-standard Higgs decays and novel collider phenomenology.

Massive color-octet bosons: bounds on effects in top-quark pair production

A critical survey of the existing direct and indirect constraints on massive spin-one color octets is presented. Since such new degrees of freedom appear in any extension of the color gauge group to a product of at least two SU(3) factors, we keep our discussion as independent as possible from the underlying theory. In the framework of scenarios that involve flavor non-universal couplings, we show that excessive flavor-changing neutral currents can be avoided by a suitable alignment in flavor space. Constraints from electroweak precision observables and direct production at hadron colliders still leave space for sizable new-physics effects in top-quark pair production, in particular a large forward-backward asymmetry. In this context, we derive a model-independent upper bound on the asymmetry that applies whenever top-antitop production receives the dominant corrections from s-channel exchange of a new single color-octet resonance.

The timing of epigenetic gold mineralization on the Baie Verte Peninsula, Newfoundland, Canada: new evidence from Re–Os pyrite geochronology

The absolute timing of epigenetic mineralization, including most types of gold deposits, is difficult to resolve due to the absence of suitable minerals in veins and replacement zones. However, gold is commonly closely associated with pyrite and arsenopyrite, which may be amenable to Re–Os geochronology, providing sufficient Re and Os are present within them. This short paper outlines the use of this method to date two gold deposits in Newfoundland using pyrite. Although the Os contents of the pyrites are extremely low (≪0.1 ppb), the Os is almost exclusively radiogenic 187Os, and data are amenable to model age calculations, as used in Re–Os molybdenite dating. The pyrites from these deposits correspond to low-level highly radiogenic sulphides, as defined by other studies. The Stog’er Tight and Pine Cove gold deposits yield mean Re–Os model ages of 411 ± 7 Ma (n = 4) and 420 ± 7 Ma (n = 5), respectively, which agree with isochron regression of 187Os against 187Re. The Re–Os age for Stog’er Tight is within uncertainty of a previous U–Pb age from ‘hydrothermal’ zircon (420 ± 5 Ma) in spatially related alteration. A latest Silurian–earliest Devonian age for the mineralization is consistent with indirect age constraints from some other gold deposits in central Newfoundland and suggests a broad temporal link to the mid-Silurian Salinic Orogeny. However, the gold mineralization appears to be younger than most plutonic activity associated with this event. The results illustrate the potential value of Re–Os pyrite geochronology in understanding the temporal framework of epigenetic mineralization, especially if future improvements in analytical precision and reductions in procedural blanks allow wider application to material with similarly low Re and Os concentrations.

Constraints on a nonthermal history from Galactic dark matter spikes

In this paper we examine whether indirect detection constraints on dark matter associated with a non-thermal history may be significantly improved when accounting for the presence of galactic substructure in the form of dark matter spikes. We find that significant constraints may be derived from the non-observation of an excess of diffuse gamma-rays and from the properties of bright gamma-ray point sources observed by the Fermi Gamma-Ray Space Telescope, but these constraints depend sensitively on the details of the formation of the first stars and their subsequent black hole remnants. However, we also find that, especially if WIMPs annihilate primarily to quarks or gauge bosons, it is possible to extract meaningful and conservative bounds on the annihilation cross section.