Search

Despite the robust cosmological and astrophysical evidence confirming the existence of a non-baryonic matter component in the Universe, the underlying nature of Dark Matter (DM) remains a mystery. Among the several possible scenarios, light DM candidates thermally produced in the early Universe are especially interesting, since their abundance could be set via the standard freeze-out mechanism. Additionally, new light states can present a rich phenomenology and are attracting increasing attention due to recent experimental capabilities to probe dark sectors with feeble interactions. In particular, inelastic DM (iDM) candidates are an appealing option, since they can avoid cosmic microwave background (CMB) radiation bounds as well as indirect and direct detection searches. Although such models have been intensively studied in the literature, the usual scenario is to consider a secluded dark photon mediator. In this work, we consider the case of iDM with general vector mediators and explore the consequences of such a choice in the relic density computation, as well as for the cosmological and experimental bounds. We examine models with couplings to baryon and lepton number and show new viable parameter regions for inelastic dark matter models. Especially, anomaly-free gauge groups with non-universal couplings to leptons open new windows of the parameter space for thermal dark matter yet unexplored by experiments. We also provide a numerical Python library to compute the relic densities for user-defined gauge charges., Comment: 47 pages, 14 figures; v2: added references, included new appendices and figures; the ReD-DeLiVeR code is available at https://github.com/anafoguel/ReD-DeLiVeR

We examine how the existence of a population of primordial black holes (PBHs) influences cosmological gravitational particle production (CGPP) for spin-0 and spin-1 particles. In addition to the known effects of particle production and entropy dilution resulting from PBH evaporation, we find that the generation of dark matter (DM) through CGPP is profoundly influenced by a possible era of PBH matter domination. This early matter dominated era results in an enhancement of the particle spectrum from CGPP. Specifically, it amplifies the peak comoving momentum $k_\star$ for spin-1 DM, while enhancing the plateau of the spectrum for minimally coupled spin-0 particles for low comoving momenta. At the same time, the large entropy dilution may partially or completely compensate for the increase of the spectrum and strongly mitigates the DM abundance produced by CGPP. Our results show that, in the computation of the final abundance, CGPP and PBH evaporation cannot be disentangled, but the parameters of both sectors must be considered together to obtain the final result. Furthermore, we explore the potential formation of PBHs from density fluctuations arising from CGPP and the associated challenges in such a scenario., Comment: 25 pages + 2 apendices; v2: expanded discussion of CGPP and minor modifications. Accepted in JCAP

We investigate the possibility of using the Short-Baseline Near Detector (SBND) at Fermilab to constrain lepton flavor violating decays of pions and kaons. We study how to leverage SBND-PRISM, the use of the neutrino beam angular spread to mitigate systematic uncertainties, to enhance this analysis. We show that SBND-PRISM can put stringent limits on the flavor violating branching ratios $\rm{BR}(\pi^+ \to \mu^+ \nu_e) = 8.9 \times 10^{-4}$, $\rm{BR}(K^+ \to \mu^+ \nu_e) = 3.2 \times 10^{-3}$, improving previous constraints by factors 9 and 1.25, respectively. We also estimate the SBND-PRISM sensitivity to lepton number violating decays, $\rm{BR}(\pi^+ \to \mu^+ \overline{\nu}_e)= 2.1 \times 10^{-3}$ and $\rm{BR}(K^+ \to \mu^+ \overline{\nu}_e) = 7.4 \times 10^{-3}$, though not reaching previous BEBC limits. Last, we identify several ways how the SBND collaboration could improve this analysis., Comment: 7 pages, 3 figures

We revisit a method for determining the neutrino mass ordering by using precision measurements of the atmospheric $\Delta m^2$'s in both electron neutrino and muon neutrino disappearance channels, proposed by the authors in 2005 (hep-ph/0503283). The mass ordering is a very important outstanding question for our understanding of the elusive neutrino and determination of the mass ordering has consequences for other neutrino experiments. The JUNO reactor experiment will start data taking this year, and the precision of the atmospheric $\Delta m^2$'s from electron anti-neutrino measurements will improve by a factor of three from Daya Bay's 2.4 % to 0.8 % within a year. This measurement, when combined with the atmospheric $\Delta m^2$'s measurements from T2K and NOvA for muon neutrino disappearance, will contribute substantially to the $\Delta \chi^2$ between the two remaining neutrino mass orderings. In this paper we derive a mass ordering sum rule that can be used to address the possibility that JUNO's atmospheric $\Delta m^2$'s measurement, when combined with other experiments in particular T2K and NOvA, can determine the neutrino mass ordering at the 3 $\sigma$ confidence level within one year of operation. For a confidence level of 5 $\sigma$ in a single experiment we will have to wait until the middle of the next decade when the DUNE experiment is operating., Comment: 7 pages, 2 figures

In this letter we show that pseudoscalar meson leptonic decay data can be used to set stringent limits on the mass $m_{W_R}$ of a right-handed vector boson, such as the one that appears in left-right symmetric models. We have shown that for a heavy neutrino with a mass $m_N$ in the range $50

In this paper we study the present and future sensitivities of the rare meson decay facilities KOTO, LHCb and Belle II to a light dark sector of the minimal dark abelian gauge symmetry where a dark Higgs $S$ and a dark photon $Z_D$ have masses $\lesssim 10$ GeV. We have explored the interesting scenario where $S$ can only decay to a pair of $Z_D$'s and so contribute to visible or invisible signatures, depending on the life-time of the latter. Our computations show that these accelerator experiments can access the dark Higgs (mass and scalar mixing) and the dark photon (mass and kinetic mixing) parameters in a complementary way. We have also discussed how the CMS measurement of the SM Higgs total decay width and their limit on the Higgs invisible branching ratio can be used to extend the experimental reach to dark photon masses up to $\sim 10$ GeV, providing at the same time sensitivity to the gauge coupling associated with the broken dark abelian symmetry., Comment: 34 pages, 11 figures; v2: minor modifications, matches version published in JHEP

We explore the neutrino sector of the minimal left-right symmetric model, with the additional charge conjugation discrete symmetry, in the tuned regime where type-I and type-II seesaw mechanisms are equally responsible for the light neutrino masses. We show that unless the charged lepton mixing matrix is the identity and the right handed neutrino mass matrix has no phases, we expect sizable lepton flavor violation and electron dipole moment in this region. We use results from recent neutrino oscillation fits, bounds on neutrinoless double beta decay, $\mu \to e \gamma$, $\mu \to 3 e$, $\mu \to e$ conversion in nuclei, the muon anomalous magnetic moment, the electron electric dipole moment and cosmology to determine the viability of this region. We derive stringent limits on the heavy neutrino masses and mixing angles as well as on the vacuum expectation value $v_L$, which drives the type-II seesaw contribution, using the current data. We discuss the perspectives of probing the remaining parameter space by future experiments., Comment: 60 pages, 26 figures

High energy collisions at the High-Luminosity Large Hadron Collider (LHC) produce a large number of particles along the beam collision axis, outside of the acceptance of existing LHC experiments. The proposed Forward Physics Facility (FPF), to be located several hundred meters from the ATLAS interaction point and shielded by concrete and rock, will host a suite of experiments to probe Standard Model (SM) processes and search for physics beyond the Standard Model (BSM). In this report, we review the status of the civil engineering plans and the experiments to explore the diverse physics signals that can be uniquely probed in the forward region. FPF experiments will be sensitive to a broad range of BSM physics through searches for new particle scattering or decay signatures and deviations from SM expectations in high statistics analyses with TeV neutrinos in this low-background environment. High statistics neutrino detection will also provide valuable data for fundamental topics in perturbative and non-perturbative QCD and in weak interactions. Experiments at the FPF will enable synergies between forward particle production at the LHC and astroparticle physics to be exploited. We report here on these physics topics, on infrastructure, detector, and simulation studies, and on future directions to realize the FPF's physics potential., Comment: 429 pages, contribution to Snowmass 2021

Axionlike particles are among the most studied extensions of the standard model. In this Letter we study the bounds that the ArgoNeuT experiment can put on the parameter space of two specific scenarios: leptophilic axionlike particles and Majorons. We find that such bounds are currently the most constraining ones in the (0.2 - 1.7) GeV mass range., Comment: 8 pages, 4 figures; v2: extended discussion of the analysis and new appendices; matches version published at PRL

Abelian U(1) gauge group extensions of the Standard Model represent one of the most minimal approaches to solve some of the most urgent particle physics questions and provide a rich phenomenology in various experimental searches. In this work, we focus on baryophilic vector mediator models in the MeV-to-GeV mass range and, in particular, present, for the first time, gauge vector field decays into almost arbitrary hadronic final states. Using only very little theoretical approximations, we rigorously follow the vector meson dominance theory in our calculations. We study the effect on the total and partial decay widths, the branching ratios, and not least on the present (future) experimental limits (reach) on (for) the mass and couplings of light vector particles in different models. We compare our results to current results in the literature. Our calculations are publicly available in a python package to compute various vector particle decay quantities in order to describe leptonic as well as hadronic decay signatures for experimental searches., Comment: 43 pages, 22 figures; DeLiVeR code available at https://github.com/preimitz/DeLiVeR ; v2: minor modifications, inclusion of error estimate section, new limits and references; matches version accepted for publication in JHEP

This review demonstrates the unique role of the neutrino by discussing in detail the physics of and with neutrinos. We deal with neutrino sources, neutrino oscillations, absolute masses, interactions, the possible existence of sterile neutrinos, and theoretical implications. In addition, synergies of neutrino physics with other research fields are found, and requirements to continue successful neutrino physics in the future, in terms of technological developments and adequate infrastructures, are stressed., Comment: 227 pages; this review of the field of neutrino physics emerged from a report written by a panel on the request of IUPAP (International Union of Pure and Applied Physics). The mandate, the panel members and the report can be found on the web page of the panel at ht tps://www.iupapneutrinopanel.org

The flagship measurement of the JUNO experiment is the determination of the neutrino mass ordering. Here we revisit its prospects to make this determination by 2030, using the current global knowledge of the relevant neutrino parameters as well as current information on the reactor configuration and the critical parameters of the JUNO detector. We pay particular attention to the non-linear detector energy response. Using the measurement of $\theta_{13}$ from Daya Bay, but without information from other experiments, we estimate the probability of JUNO determining the neutrino mass ordering at $\ge$ 3$\sigma$ to be 31% by 2030. As this probability is particularly sensitive to the true values of the oscillation parameters, especially $\Delta m^2_{21}$, JUNO's improved measurements of $\sin^2 \theta_{12}$, $\Delta m^2_{21}$ and $|\Delta m^2_{ee}|$, obtained after a couple of years of operation, will allow an updated estimate of the probability that JUNO alone can determine the neutrino mass ordering by the end of the decade. Combining JUNO's measurement of $|\Delta m^2_{ee}|$ with other experiments in a global fit will most likely lead to an earlier determination of the mass ordering., Comment: 31 pages, 15 figures, many with multiple panels

We inspect recently updated neutrino oscillation data -- specifically coming from the Tokai to Kamioka and NuMI Off-axis $\nu_e$ Appearance experiments -- and how they are analyzed to determine whether the neutrino mass ordering is normal ($m_1 < m_2 < m_3$) or inverted ($m_3 < m_1 < m_2$). We show that, despite previous results giving a strong preference for the normal ordering, with the newest data from T2K and NOvA, this preference has all but vanished. Additionally, we highlight the importance of this result for non-oscillation probes of neutrinos, including neutrinoless double beta decay and cosmology. Future experiments, including JUNO, DUNE, and T2HK will provide valuable information and determine the mass ordering at a high confidence level., Comment: 5 pages, 3 figures + 1 appendix (1 figure). Updated NOvA analysis, matches published version

We comment on Daya Bay's latest definition of the effective Delta m^2 for short baseline reactor electron antineutrino disappearance experiments used in arXiv:1809.02261 (Phys. Rev. Lett. 121, no. 24, 241805 (2018)), Comment: 1.5 pages, 1 figure

Novel leptophilic neutral currents can be tested at upcoming neutrino oscillation experiments using two complementary processes, neutrino trident production and neutrino-electron ($\nu-e$) elastic scattering. Considering generic anomaly-free $U(1)$ extensions of the Standard Model, we discuss the characteristics of $\nu-e$ scattering as well as $e^+e^-$ and $\mu^+\mu^-$ trident production at the DUNE near detector in the presence of such BSM scenarios. We then determine the sensitivity of DUNE in constraining the well-known $L_e - L_\mu$ and $L_\mu - L_\tau$ models. We conclude that DUNE will be able to probe these leptophilic models with unprecedented sensitivity, covering unproved explanations of the $(g-2)_\mu$ discrepancy., Comment: 32 pages, 10 figures

Neutrinos may be the harbingers of new dark sectors, since the renormalizable neutrino portal allows for their interactions with hidden new physics. We propose here to use this fact to connect the generation of neutrino masses to a light dark sector, charged under a new $U(1)_{\cal D}$ dark gauge symmetry. We introduce the minimal number of dark fields to obtain an anomaly free theory with spontaneous breaking of the dark symmetry, and obtain automatically the inverse seesaw Lagrangian. In addition, the so-called $\mu$-term of the inverse seesaw is dynamically generated and technically natural in this framework. As a bonus, the new light dark gauge boson can provide a possible explanation to the MiniBooNE anomaly., Comment: 7 pages, 1 figure, published version in Phys. Lett. B

Neutrino trident scattering is a rare Standard Model process where a charged-lepton pair is produced in neutrino-nucleus scattering. To date, only the dimuon final-state has been observed, with around 100 total events, while the other channels are as yet unexplored. In this work, we compute the trident production cross section by performing a complete four-body phase space calculation for different hadronic targets. This provides a correct estimate both of the coherent and the diffractive contributions to these cross sections, but also allows us to address certain inconsistencies in the literature related to the use of the Equivalent Photon Approximation in this context. We show that this approximation can give a reasonable estimate only for the production of dimuon final-states in coherent scattering, being inadmissible for all other cases considered. We provide estimates of the number and distribution of trident events at several current and future near detector facilities subjected to intense neutrino beams from accelerators: five liquid-argon detectors (SBND, $\mu$BooNE, ICARUS, DUNE and $\nu$STORM), the iron detector of T2K (INGRID) and three detectors made of composite material (MINOS, NO$\nu$A and MINER$\nu$A). We find that for many experiments, trident measurements are an attainable goal and a valuable addition to their near detector physics programme., Comment: 44 pages, 11 figures

We present a novel framework that provides an explanation to the long-standing excess of electron-like events in the MiniBooNE experiment at Fermilab. We suggest a new dark sector containing a dark neutrino and a dark gauge boson, both with masses between a few tens and a few hundreds of MeV. Dark neutrinos are produced via neutrino-nucleus scattering, followed by their decay to the dark gauge boson, which in turn gives rise to electron-like events. This mechanism provides an excellent fit to MiniBooNE energy spectra and angular distributions., Comment: 5 pages, 3 figures, discussion on constraints expanded, corrected figure and benchmark point updated, matches PRL version

We investigate the sensitivity of IceCube(-Gen2) to a scalar leptoquark scenario with couplings only to heavy quark flavors which may be connected to solving discrepancies in $B$-meson semileptonic decays. We take into account, for the first time, the non-negligible neutrino-gluon cross section induced by leptoquarks, and we systematically account for indirect and direct constraints which have been overlooked in previous studies. We conclude that IceCube(-Gen2) can only probe the light LQ regime, already disfavored by the combination of flavor physics constraints, electroweak precision data and the direct searches at the LHC., Comment: 30 pages, 14 figures; references added, accepted for publication in JHEP

The detection of coherent neutrino-nucleus scattering by the COHERENT collaboration has set on quantitative grounds the existence of an irreducible neutrino background in direct detection searches of Weakly Interacting Massive Dark Matter candidates. This background leads to an ultimate discovery limit for these experiments: a minimum Dark Matter interaction cross section below which events produced by the coherent neutrino scattering will mimic the Dark Matter signal, the so-called \emph{neutrino floor}. In this work we study the modification of such neutrino floor induced by non-standard neutrino interactions within their presently allowed values by the global analysis of oscillation and COHERENT data. By using the full likelihood information of such global analysis we consistently account for the correlated effects of non-standard neutrino interactions both in the neutrino propagation in matter and in its interaction in the detector. We quantify their impact on the neutrino floor for five future experiments: DARWIN (Xe), ARGO (Ar), Super-CDMS HV (Ge and Si) and CRESST phase III (CaWO$_4$). Quantitatively, we find that non-standard neutrino interactions allowed at the $3\sigma$ level can result in an increase of the neutrino floor of up to a factor $\sim 5$ with respect to the Standard Model expectations and impact the expected sensitivities of the ARGO, CRESST phase III and DARWIN experiments., Comment: 21 pages, 4 figures. Matches version published in the JHEP. Corrected exposure and results for CRESST phase III

We discuss the effect of Beyond the Standard Model charged current interactions on the detection of the Cosmic Neutrino Background by neutrino capture on tritium in a PTOLEMY-like detector. We show that the total capture rate can be substantially modified for Dirac neutrinos if scalar or tensor right-chiral currents, with strength consistent with current experimental bounds, are at play. We find that the total capture rate for Dirac neutrinos, $\Gamma_{\rm D}^{\rm BSM}$, can be between 0.3 to 2.2 of what is expected for Dirac neutrinos in the Standard Model, $\Gamma_{\rm D}^{\rm SM}$, so that it can be made as large as the rate expected for Majorana neutrinos with only Standard Model interactions. A non-negligible primordial abundance of right-handed neutrinos can only worsen the situation, increasing $\Gamma_{\rm D}^{\rm BSM}$ by 30 to 90\%. On the other hand, if a much lower total rate is measured than what is expected for $\Gamma_{\rm D}^{\rm SM}$, it may be a sign of new physics., Comment: Version published in JHEP. Some comments and references added

In Neutrinophilic Two Higgs Doublet Models, Dirac neutrino masses are obtained by forbidding a Majorana mass term for the right-handed neutrinos via a symmetry. We study a variation of such models in which that symmetry is taken to be a local U(1), leading naturally to the typical Lagrangian of the inverse seesaw scenario. The presence of a new gauge boson and of an extended scalar sector result in a rich phenomenology, including modifications to Z, Higgs and kaon decays as well as to electroweak precision parameters, and a pseudoscalar associated to the breaking of lepton number., Comment: 21 pages, 2 figures, matches the published version in JHEP

We study the contributions of colorless vectorlike fermions to the triple gauge couplings $W^+ W^- \gamma$ and $W^+ W^- Z^0$. We consider models in which their coupling to the Standard Model Higgs boson is allowed or forbidden by quantum numbers. We assess the sensitivity of the future accelerators FCC-ee, ILC and CLIC to the parameters of these models, assuming they will be able to constrain the anomalous triple gauge couplings with a precision $\delta \kappa_V \sim \mathcal{O}(10^{-4})$, $V=\gamma,Z^0$. We show that the combination of measurements at different center-of-mass energies helps to improve the sensitivity to the contribution of vectorlike fermions, in particular when they couple to the Higgs. In fact, the measurements at the FCC-ee and, especially, the ILC and the CLIC, may turn the triple gauge couplings into a new set of precision parameters able to constrain the models better than the oblique parameters or the $H \to \gamma \gamma$ decay, even assuming the considerable improvement of the latter measurements achievable at the new machines., Comment: Matches version published in PRD. Some references added and LHC limits included

We investigate the effect of new physics interacting with both Dark Matter (DM) and neutrinos at DM direct detection experiments. Working within a simplified model formalism, we consider vector and scalar mediators to determine the scattering of DM as well as the modified scattering of solar neutrinos off nuclei. Using existing data from LUX as well as the expected sensitivity of LUX-ZEPLIN and DARWIN, we set limits on the couplings of the mediators to quarks, neutrinos and DM. Given the current limits, we also assess the true DM discovery potential of direct detection experiments under the presence of exotic neutrino interactions. In the case of a vector mediator, we show that the DM discovery reach of future experiments is affected for DM masses $m_\chi \lesssim 10$ GeV or DM scattering cross sections $\sigma_\chi \lesssim 10^{-47}$ cm$^2$. On the other hand, a scalar mediator will not affect the discovery reach appreciably., Comment: One figure, comments and references added. Version published in the JHEP. V3: eq. 3.4 corrected, numerical results unchanged

We discuss weak kaon decays in a scenario in which the Standard Model is extended by massive sterile fermions. After revisiting the analytical expressions for leptonic and semileptonic decays we derive the expressions for decay rates with two neutrinos in the final state. By using a simple effective model with only one sterile neutrino, compatible with all current experimental bounds and general theoretical constraints, we conduct a thorough numerical analysis which reveals that the impact of the presence of massive sterile neutrinos on kaon weak decays is very small, less than $1\%$ on decay rates. The only exception is $\mathcal{B} (K_L\to \nu\nu)$, which can go up to $\mathcal{O}( 10^{-10})$, thus possibly within the reach of the KOTO experiment. In other words, if all the future measurements of weak kaon decays turn out to be compatible with the Standard Model predictions, this would not rule out the existence of massive light sterile neutrinos with non-negligible active-sterile mixing. Instead, for a sterile neutrino of mass below $m_K$, one might obtain a huge enhancement of $\mathcal{B} (K_L\to \nu\nu)$, otherwise negligibly small in the Standard Model., Comment: 32 pages, 11 plots in 6 figures, version published in PRD

We examine various scenarios that involve a light ${\cal O}(1 TeV)$ leptoquark state and select those which are compatible with the current experimental values for $\mathcal{B}(B_s\to \mu\mu)$, $\mathcal{B}(B\to K\mu\mu)_{\mathrm{large}-q^2}$, $R_K=\mathcal{B^\prime}(B\to K\mu\mu)/\mathcal{B^\prime}(B\to Kee)$, and which lead to predictions consistent with other experimental data. We show that two such scenarios are phenomenologically plausible, namely the one with a doublet of scalar leptoquarks of hypercharge $1/6$, and the one with a triplet of vector leptoquarks of hypercharge $2/3$. We also argue that a model with a singlet scalar leptoquark of hypercharge $1/3$ is not viable. Using the present experimental data as constraints, it is shown that the exclusive lepton flavor violating decays, $\mathcal{B}(B_s\to \mu\tau)$, $\mathcal{B}(B\to K \mu\tau)$ and $\mathcal{B}(B\to K^\ast \mu\tau)$, can be as large as $\mathcal{O}(10^{-5})$., Comment: 30p (published version), Interference term in Eq.(31) fixed

Flavor ratios of very high energy astrophysical neutrinos, which can be studied at the Earth by a neutrino telescope such as IceCube, can serve to diagnose their production mechanism at the astrophysical source. The flavor ratios for neutrinos and antineutrinos can be quite different as we do not know how they are produced in the astrophysical environment. Due to this uncertainty the neutrino and antineutrino flavor ratios at the Earth also could be quite different. Nonetheless, it is generally assumed that flavor ratios for neutrinos and antineutrinos are the same at the Earth, in fitting the high energy astrophysical neutrino data. This is a reasonable assumption for the limited statistics for the data we currently have. However, in the future the fit must be performed allowing for a possible discrepancy in these two fractions in order to be able to disentangle different production mechanisms at the source from new physics in the neutrino sector. To reinforce this issue, in this work we show that a wrong assumption about the distribution of neutrino flavor ratios at the Earth may indeed lead to misleading interpretations of IceCube results., Comment: V2: 19 pages, 7 figures, improved discussion, to appear in JCAP

Starting from the general effective hamiltonian relevant to the $b\to s$ transitions, we derive the expressions for the full angular distributions of the $B \to K^{(\ast )} \ell_1 \ell_2$ decay modes, as well as for ${\cal B}(B_s \to \ell_1\ell_2 )$ ($\ell_1\neq \ell_2$). We point out the differences in the treatment of the lepton flavor violating modes with respect to the lepton flavor conserving ones. Concerning the relevant Wilson coefficients we evaluate them in two different scenarios: (i) The (pseudo-)scalar coefficients are obtained using the (pseudo-)scalar coupling extracted from the experimental non-zero value of ${\cal B}(h\to \mu\tau)$, (ii) Revisiting a $Z^\prime$-model in which the flavor changing neutral couplings are allowed. We provide the numerical estimates of the branching fractions of the above-mentioned modes in both scenarios., Comment: 20p [published version], typo in Eq.(9) corrected

A plausible explanation of the recent experimental indication of a resonance in the two-photon spectrum at LHC is that it corresponds to the CP-odd Higgs boson. We explore such a possibility in a generic framework of the two Higgs doublet models (2HDM), and combine $m_A \approx 750$GeV with the known $m_h =125.7(4)$~GeV to show that the charged Higgs boson and the other CP-even scalar masses become bounded from bellow and from above. We show that this possibility is also consistent with the electroweak precision data and the low energy observables, which we test in a few leptonic and semileptonic decay modes., Comment: 16 pages, published version

We derive stringent limits on neutrinophilic two-Higgs-doublet models from low-energy observables after the discovery of the Higgs boson and of the mixing angle $\theta_{13}$. These decays can constrain the plane spanned by $m_{H^\pm}$, the mass of the new charged Higgs, and $v_2$, the vacuum expectation value of the new neutrinophilic scalar doublet. Lepton flavor conserving decays are not able to set meaningful bounds, since they depend strongly on the unknown neutrino absolute mass scale. On the other hand, loop induced lepton flavor violating decays, such as $\mu \to e \gamma$, $\mu \to 3 e $ or $\mu \to e$ in nuclei are currently responsable for the best limits today. If $v_2 \lesssim 1 \, (0.1)$ eV we get $m_{H^\pm} \gtrsim 250 \, (2500)$ GeV at 90% CL. In the foreseen future these limits can improve by at least a factor of 100., Comment: 15 pages, 5 figures, references and comments added, conclusions unchanged, matches version to appear in JHEP

In composite Higgs models the pseudo-Nambu-Goldstone Boson (pNGB) nature of the Higgs field is an interesting alternative for explaning the smallness of the electroweak scale with respect to the beyond the Standard Model scale. In non-minimal models additional pNGB states are present and can be a Dark Matter (DM) candidate, if there is an approximate symmetry suppressing their decay. Here we assume that the low energy effective theory (for scales much below the compositeness scale) corresponds to the Standard Model with a pNGB Higgs doublet and a pNGB DM multiplet. We derive general effective DM Lagrangians for several possible DM representations (under the SM gauge group), including the singlet, doublet and triplet cases. Within this framework we discuss how the DM observables (relic abundance, direct and indirect detection) constrain the dimension-6 operators induced by the strong sector assuming that DM behaves as a Weakly Interacting Particle (WIMP) and that the relic abundance is settled through the freeze-out mechanism. We also apply our general results to two specific cosets: $SO(6)/SO(5)$ and $SO(6)/SO(4) \times SO(2)$, which contain a singlet and doublet DM candidate, respectively. In particular we show that if compositeness is a solution to the little hierarchy problem, representations larger than the triplet are strongly disfavored. Furthermore, we find that composite models can have viable DM candidates with much smaller direct detection cross-sections than their non-composite counterparts, making DM detection much more challenging., Comment: version accepted by JHEP

We discuss possible interpretations of the 37 high energy neutrino events observed by the IceCube experiment in the South Pole. We examine the possibility to explain the observed neutrino spectrum exclusively by the decays of a heavy long-lived particle of mass in the PeV range. We compare this with the standard scenario, namely, a single power-law spectrum related to neutrinos produced by astrophysical sources and a viable hybrid situation where the spectrum is a product of two components: a power-law and the long-lived particle decays. We present a simple extension of the Standard Model that could account for the heavy particle decays that are needed in order to explain the data. We show that the current data equally supports all above scenarios and try to evaluate the exposure needed in order to falsify them in the future., Comment: 29 pages, 9 figures; Re-analysis to include higher energy bins resulting in slight changes in numerics and figures while the conclusions remain unaffected. References updated and typos corrected to match the published version

These lecture notes are based on a course given at Institut de Physique Th\'eorique of CEA/Saclay in January/February 2013.

We analyze the behavior of Higgs to diphoton rate and Higgs gluon-gluon production cross section in minimal extensions of the Standard Model comprising new colored vector-like fermions that do not mix with the ordinary ones. We compare these information with constraints coming from electroweak precision measurements. We compute pair production cross sections for the lightest fermion and discuss the LHC bounds. Finally, we study the phenomenology of possible quarkonium states composed by these new colored fermions., Comment: 18 pages, 7 figures. v2: typos fixed, references added, small improvements made

We analyse the interplay between the Higgs to diphoton rate and electroweak precision measurements contraints in extensions of the Standard Model with new uncolored charged fermions that do not mix with the ordinary ones. We also compute the pair production cross sections for the lightest fermion and compare them with current bounds., Comment: 19 pgs, 10 figures, typos fixed, reference added, small improvements made

We show how one could determine the neutrino mass hierarchy with Mossbauer neutrinos and also revisit the question of whether the hierarchy can be determined with reactor neutrinos., Comment: contribution to NOW 2008, 3 pages, 4 figures, latex

We investigate what one can hope to learn about the parameters that describe the neutrino fluxes emitted by the explosion of a galactic supernova using the observations of a megaton-size Water-Cherenkov detector. We calculate the allowed regions that can be obtained by fitting these parameters to a simulated observation of events by such a detector. All four available detection channels (inverse beta decay, charge and neutral current on oxygen and elastic scattering on electrons) are included in the fit and we use a ten dimensional parameters space. Nine parameters describe the initial neutrino fluxes and are referred to as the supernova parameters. Furthermore, we include the dependence on the Chooz mixing angle $\theta_{13}$, which controls the matter effects that the neutrino undergoes in the outer-parts of the supernova. If we do not make any extra assumption on these parameters, we show that one can hope to determine $\theta_{13}$ quite well whereas, except for the parameters describing the $\bar\nu_e$ flux, most of the supernova parameters are rather difficult to constrain, even if the four detection channels could be completely separated., Comment: 17 pages. References added and updated, additions in acknowledgment

The neutrino mass hierarchy can be determined, in principle, by measuring a phase in the disappearance oscillation probability in vacuum, without relying on the matter effect, using a single channel. This phase is not the same for the normal and inverted neutrino mass spectra. In this paper, we give a complete description and physics understanding of the method. The key feature of the method is to detect advancement (normal) or retardation (inverted) of the phase of the atmospheric-scale oscillation relative to the solar-scale oscillation. We then show that this method can be realized with the recently proposed resonant $\bar{\nu}_{e}$ absorption reaction enhanced by M\"ossbauer effect. The unique feature of this setup is the ultra-monochromaticity of the observed \bar{\nu}_{e}'s. Because of this feature the phase advancement or retardation of atmospheric-scale neutrino oscillation is detectable after 20 or more oscillations if the source and the target are made sufficiently compact in size. A quantitative estimate of the sensitivity to mass hierarchy resolution is given. We have also examined how a possible continuation of such experiment can be carried out in order also to achieve high precision (few %) determination of the solar-scale oscillation parameters \Delta m^2_{21} and \theta_{12}., Comment: 23 pages, 10 figures, final published version, title changed

We investigate the sensitivity of some of the proposed next-generation neutrino experiments to a galactic supernova. In particular, we study how well the supernova parameters (the average energies and luminosities) can be separated from the unknown neutrino oscillation parameters ($\theta_{13}$ and the neutrino mass hierarchy). Three types of experiments, all in the 100-kton class, are compared. These are: a 540 kton water-Cherenkov detector, a 100 kton liquid Argon detector and a 50 kton scintillator detector. We demonstrate that practically all of these proposed detectors have the possibility to determine the hierarchy of the neutrino masses if the angle $\theta_{13}$ is sufficiently large ($\sin^2(\theta_{13}) > 10^{-4}$) and the hierarchy of the average energies is larger than about 20%. They can at the same time determine some of the supernova parameters well. The average energy of the $\nu_\mu$ and $\nu_\tau$ species can be determined within 5% uncertainty in most of the parameter space suggested by supernova simulations. The detection of several separable channels measuring different combinations of charged current and neutral current processes is crucial for determining the value of $\theta_{13}$ and the hierarchy. However, there are cases where a few of the SN parameters can be determined rather well even if only the main charged current detection channel is available., Comment: 44 pages, 13 figures. Appendix added and improvements in text. Matches published version

Mixing of active neutrinos with sterile ones generate ``induced'' contributions to the mass matrix of active neutrinos $\sim m_S \sin^2\theta_{aS}$, where $m_S$ is the Majorana mass of the sterile neutrino and $\theta_{aS}$ is the active-sterile mixing angle. We study possible effects of the induced matrix which can modify substantially the implications of neutrino oscillation results. We have identified the regions of $m_S$ and $\sin^2\theta_{aS}$ where the induced matrix (i) provides the dominant structures, (ii) gives the sub-dominant effects and (iii) where its effects can be neglected. The induced matrix can be responsible for peculiar properties of the lepton mixing and neutrino mass spectrum, in particular, it can generate the tri-bimaximal mixing. We update and discuss bounds on the induced masses from laboratory measurements, astrophysics and cosmology. We find that substantial impact of the induced matrix is possible if $m_S \sim 0.1-1$ eV and $\sin^2\theta_{aS} \sim 10^{-3} - 10^{-2}$ or $m_S \geq 200$ MeV and $\sin^2\theta_{aS} \leq 10^{-9}$. The bounds can be relaxed in cosmological scenarios with low reheating temperature, if sterile neutrinos decay sufficiently fast, or their masses change with time., Comment: Figures updated, version to be published in Phys. Rev. D

If the lepton mixing angle theta_{23} is not maximal, there arises a problem of ambiguity in determining theta_{23} due to the existence of two degenerate solutions, one in the first and the other in the second octant. We discuss an experimental strategy for resolving the theta_{23} octant degeneracy by combining reactor measurement of theta_{13} with accelerator nu_{mu} disappearance and nu_{e} appearance experiments. The robustness of the theta_{23} degeneracy and the difficulty in lifting it only by accelerator experiments with conventional nu_{mu} (and nu_{mu}-bar) beam are demonstrated by analytical and numerical treatments. Our method offers a way to overcome the difficulty and can resolve the degeneracy between solutions sin^2 theta_{23} = 0.4 and sin^2 theta_{23} = 0.6 if sin^2 (2 theta_{13}) \gsim 0.05 at 95% CL by assuming the T2K phase II experiment and a reactor measurement with an exposure of 10 GW.kt.yr. The dependence of the resolving power of the octant degeneracy on the systematic errors of reactor experiments is also examined., Comment: 23 pages, 9 figures, version to appear in PRD

We give a brief report on our recent paper, hep-ph/0601198, in which we calculate the nu_2 mass eigenstate purity of B^8 solar neutrinos as 91 +/- 2 %., Comment: 3 pages, 2 postscript figures, latex, AIP conference style. PANIC 2005 proceedings

We calculate the fraction of B^8 solar neutrinos that arrive at the Earth as a nu_2 mass eigenstate as a function of the neutrino energy. Weighting this fraction with the B^8 neutrino energy spectrum and the energy dependence of the cross section for the charged current interaction on deuteron with a threshold on the kinetic energy of the recoil electrons of 5.5 MeV, we find that the integrated weighted fraction of nu_2's to be 91 \pm 2 % at the 95% CL. This energy weighting procedure corresponds to the charged current response of the Sudbury Neutrino Observatory (SNO). We have used SNO's current best fit values for the solar mass squared difference and the mixing angle, obtained by combining the data from all solar neutrino experiments and the reactor data from KamLAND. The uncertainty on the nu_2 fraction comes primarily from the uncertainty on the solar delta m^2 rather than from the uncertainty on the solar mixing angle or the Standard Solar Model. Similar results for the Super-Kamiokande experiment are also given. We extend this analysis to three neutrinos and discuss how to extract the modulus of the Maki-Nakagawa-Sakata mixing matrix element U_{e2} as well as place a lower bound on the electron number density in the solar B^8 neutrino production region., Comment: 23 pages, 8 postscript figures, latex. Dedicated to the memory of John Bahcall who championed solar neutrinos for many lonely years

We show that by combining high precision measurements of the atmospheric delta m^2 in both the electron and muon neutrino (or anti-neutrino) disappearance channels one can determine the neutrino mass hierarchy. The required precision is a very challenging fraction of one per cent for both measurements. At even higher precision, sensitivity to the cosine of the CP violating phase is also possible. This method for determining the mass hierarchy of the neutrino sector does not depend on matter effects., Comment: 12 pages, 3 postscript figures, latex