Heavy neutrinos with masses in the MeV range can in principle simultaneously explain the light neutrino masses and the origin of baryonic matter in the universe. The strongest constraints on their properties come from their potential impact on the formation of light elements in the early universe. Since these constraints rely on assumptions about the cosmic history, independent checks in the laboratory are highly desirable. In this paper, we discuss the opportunity to search for heavy neutrinos within the MeV mass range in short and medium baseline reactor neutrino experiments, using the SoLid, JUNO and TAO experiments as examples. These experiments can give the currently strongest upper bound on the mixing between the light electron neutrinos and the heavy neutrino in the 2-9 MeV mass range.
This paper was submitted in Russian edition of Journal Physics of Atomic Nuclei in 2001. The present status of experiments that are being performed at nuclear reactors in order to seek the neutrino masses, mixing, and magnetic moments, whose discovery would be a signal of the existence of physics beyond the Standard Model, is considered, along with their future prospects.
We show that in a reactor disappearance oscillation experiment the sensitivity to the mixing parameter can be substantially improved for $(1 - 5\cdot10^{-4}) eV^{2}$ mass parameter range which includes both the LSND and the atmospheric neutrino oscillation regions. The objectives are: to search for the sterile neutrinos and to get a better understanding of the atmospheric neutrino oscillation mechanism. The parameters of the underground (600 m.w.e.) Krasnoyarsk reactor and data from the CHOOZ reactor oscillation experiment are used to estimate the effect and background rates.
Sensitive searches for antineutrino oscillations in atmospheric mass parameter region much discussed in recent years are based on accurate comparison of the inverse beta decay positron spectra measured in two (or more) detectors, far and near, stationed e.g. at ~1000 m and ~100 m from the reactor(s). We show that antineutrinos emitted from the stored irradiated fuel can differently distort the soft part of positron spectra measured in the far and near detector and thus mimic (or hide) the oscillation signal
A nuclear reactor is a powerful tool to study neutrinos and light dark sector particles. Some of the reactor experiments have proven to be extremely useful already. Considering the great interest in the power of intensity frontier to search for new light particles, it would be desirable to explore more possibilities to exploit the existing reactor power sources for particle physics research. We suggest a new reactor experiment searching for the dark sector. The dark photon can be produced in a reactor core and decay into a photon and an axion in the presence of the dark axion portal through an…
In 2012 the Daya Bay experiment made an unambiguous observation of reactor antineutrino disappearance over kilometer-long baselines and determined that the neutrino mixing angle $θ_{13}$ is non-zero. The measurements of Daya Bay have provided the most precise determination of $θ_{13}$ to date. This whitepaper outlines the prospects for precision studies of reactor antineutrinos at Daya Bay in the coming years. This includes precision measurements of sin$^2 2θ_{13}$ and $Δm^2_{ee}$ to $<$3%, high-statistics measurement of reactor flux and spectrum, and non-standard physics searches.
We study the optimization of a green-field, two-baseline reactor experiment with respect to the sensitivity for electron antineutrino disappearance in search of a light sterile neutrino. We consider both commercial and research reactors and identify as key factors the distance of closest approach and detector energy resolution. We find that a total of 5 tons of detectors deployed at a commercial reactor with a closest approach of 25 m can probe the mixing angle $\sin^22θ$ down to $\sim5\times10^{-3}$ around $Δm^2\sim 1$ eV$^2$. The same detector mass deployed at a research reactor can be sensi…
The Daya Bay reactor experiment has reported the most precise measurement of sin$^{2}2θ_{13}$ and $Δm^{2}_{ee}$ by using a data set with the fully constructed design of 8 antineutrino detectors (ADs). We also report on a new independent measurement of sin$^{2}2θ_{13}$ from neutron capture on hydrogen, which confirms the results using gadolinium caputres. Several other analyses are also performed, including a measurements on the absolute reactor antineutrino flux and a search for light sterile neutrinos. Prospects for new analyses such as searching for CPT/LI violation at Daya Bay are ongoing.
Despite the dramatic progress made in neutrino oscillation studies recently, several fundamental neutrino parameters remain either unknown or poorly measured. We discuss in detail a method for their measurement by precision studies of oscillation-caused neutrino energy spectrum distortions, for which a large underwater inverse beta decay detector appears to be a perfect tool. Results determine optimal baselines and necessary exposures in the presence of systematic uncertainties and the unavoidable background from terrestrial antineutrinos.
New generation of three reactor neutrino experiments have made definitive measurements of the smallest neutrino mixing angle theta13 in 2012, based on the disappearance of electron antineutrinos. More precise measurements of the mixing angle have been made as well as the squared mass difference between electron neutrinos. A rather large value of theta13 has opened a new window to find the CP violation phase and to determine the neutrino mass hierarchy. Future reactor experiments, JUNO and RENO50, are proposed to determine the neutrino mass hierarchy and to make highly precise measurements of t…
Antineutrino detectors are practical, non-intrusive tools capable of remotely monitoring the activity of nuclear reactors. Here we explore the sensitivity of the Super-Kamiokande water-Cherenkov detector, following gadolinium loading, to antineutrinos from a nuclear reactor complex at a distance of approximately 190 km. The livetimes required to observe the two currently operating cores in the reactor complex depend on the activity of other reactors in the vicinity, as well as on estimates of detection efficiency and background rates. Under reasonable assumptions, we find that gadolinium-loade…
The calculations of the time-dependent reactor antineutrino energy spectrum are presented. Some problems associated with sensitive searches for neutrino magnetic moment and neutrino oscillations in reactor antineutrino flux are considered.
We present calculations of the magnetic moment contribution to neutrino electron scattering in large extra dimension brane-bulk models (LED) with three bulk neutrinos. We discuss the cases with two and three large extra dimensions of sizes $R$. The calculations are done using reactor flux from Uranium, $^{235}U$ as the neutrino source. We find that if the electron neutrino mass is chosen to be in the range of one eV, the differential cross section for $\barν-e$ scattering for low electron recoil energy can be of the same order as the presently explored values in reactor experiments. Furthermor…
Recent strong experimental evidence of a narrow exotic S = +1 baryon resonance, $Θ^+$, suggests the existence of other exotic baryons. We discuss the prospects of confirming earlier experimental evidence of $Θ^+$ and the observation of additional hypothetical exotic baryons in $e^+e^-$ annihilations and $γγ$ collisions at LEP and B Factories.
Reactor neutrino experiments provide a rich environment for the study of axionlike particles (ALPs). Using the intense photon flux produced in the nuclear reactor core, these experiments have the potential to probe ALPs with masses below 10 MeV. We explore the feasibility of these searches by considering ALPs produced through Primakoff and Compton-like processes as well as nuclear transitions. These particles can subsequently interact with the material of a nearby detector via inverse Primakoff and inverse Compton-like scatterings, via axio-electric absorption, or they can decay into photon or…
The current status of neutrino oscillation searches with reactors and accelerators is reviewed. An outlook, especially on future long baseline neutrino oscillation projects, is given.
The present status of neutrino oscillation searches with reactors and accelerators is reviewed. An outlook, especially on future long baseline neutrino oscillation projects, is given.
We discuss the prospects for charged Higgs boson searches at the LHC, within the two-Higgs-doublet models (2HDM). The 2HDM is generally less constrained than the corresponding sector of the MSSM, but there are still severe theoretical and experimental constraints that already exclude significant regions of the naive parameter space. Explicit searches in the $H^+\toτ^+ν$ and $H^+\to t\bar b$ channels are further restricting parts of the 2HDM parameter space.
The sensitivity to New Physics of a low threshold scintillating argon bubble chamber measuring coherent elastic neutrino-nucleus scattering in reactors is reported. Namely, light scalar mediators, sterile neutrino oscillations, unitarity violation, and non-standard interactions are studied. The results indicate that this detector could be able to set stronger constraints than current limits set by the recent COHERENT measurements. Considering the best scenario, a 100 kg detector located 30 m from a 2000 MW$_{th}$ reactor, a sterile neutrino search would cover most of the space parameter allowe…
We study the time evolution of the typical nuclear reactor antineutrino energy spectrum during reactor ON period and the decay of the residual antineutrino spectrum after reactor is stopped. We find that relevant variations of the soft recoil electron spectra produced via weak and magnetic ${\widetilde ν}_{e},e$ scattering process can play a signigicant role in the current and planned searches for the neutrino magnetic moment at reactors.
The current status of neutrino oscillation searches with reactors and accelerators is reviewed. An outlook, especially on future long baseline neutrino oscillation projects, is given.
We consider status of the Kr2Det project aimed at sensitive searches for neutrino oscillations in the atmospheric neutrino mass parameter region around Dm2 ~ 3x10-3 eV2and at obtaining new information on the electron neutrino mass structure (Ue3).
Searches for pseudoscalar axion-like-particles (ALPs) typically rely on their decay in beam dumps or their conversion into photons in haloscopes and helioscopes. We point out a new experimental direction for ALP probes through their production via the Primakoff process or Compton-like scattering off of electrons or nuclei. We consider ALPs produced by the intense gamma ray flux available from megawatt-scale nuclear reactors at neutrino experiments through Primakoff-like or Compton-like channels. Low-threshold detectors in close proximity to the core will have visibility to ALP decays and inver…
The installation of forward proton detectors at the LHC will provide the possibility to observe central exclusive processes, opening a novel window on physics beyond the Standard Model. We review recent developments on the discovery potential from central exclusive light-by-light scattering. The search for this process is expected to provide bounds on a wide range of particles, and turns out to be complementary from new physics searches in inclusive channels.
We examine the prospects of detecting sfermions at a gamma gamma collider. Once produced, a slepton can decay into a pair of quarks (jets) through R-parity violating interactions. Similarly, a squark may decay into a lepton-quark pair. Analyzing the corresponding Standard Model backgrounds, namely 4-jet and dilepton plus dijet final states respectively, we show that the sfermion can be detected almost right upto the kinematic limit and its mass determined to a fair degree of accuracy. Similar statements also hold for nonsupersymmetric leptoquarks and diquarks.
At hadron colliders the $γγ+jet$ channel provides larger signal-to-background ratio in comparison with inclusive $γγ$ channel in hunting for scalars uncharged under the SM gauge group. At NLO in QCD perturbation theory we evaluate selfconsistently the signal significance for the SM Higgs boson production in $γγ+jet$ channel at LHC. Three-body final state kinematics allows for refined cuts. The adjustment of these cuts increases the signal significance upto the level of inclusive channel. Applying a justified simple rescaling procedure to the results obtained for SM Higgs boson, we estimate the…
Hadron colliders are providing a unique opportunity for testing Lorentz invariance and CPT symmetry at high energy and in a laboratory. A first measurement in the top-quark sector was performed at the Tevatron. We present here prospective studies for testing Lorentz invariance in top-quark pair production at the LHC and future colliders. The b-quark sector was investigated recently at LHCb. Eventually, new bounds on photon parameters can be extracted from the observation of TeV photons at the LHC. We will conclude by highlighting other opportunities provided by hadron colliders.
Predictions of antineutrino fluxes produced by fission isotopes in a nuclear reactor have recently received increased scrutiny due to observed differences in predicted and measured inverse beta decay (IBD) yields, referred to as the 'reactor antineutrino flux anomaly.' In this paper, global fits are applied to existing IBD yield measurements to produce constraints on antineutrino production by individual plutonium and uranium fission isotopes. We find that fits including measurements from highly 235U-enriched cores and fits including Daya Bay's new fuel evolution result produce discrepant best…
This paper investigates a signature of Lorentz invariance violation with the $t\bar{t}$ production at the LHC and future hadron colliders. Possible deviations from the Lorentz symmetry remain poorly constrained in the top quark sector. With a dedicated analysis of $t\bar{t}$ events produced at the LHC, bounds in the top sector can be improved by up to three orders of magnitude relative to Tevatron, the only measurement existing so far. The sensitivity will be even further enhanced at the HL-LHC and future colliders.
In this article we study the prospects of the proposed Large Hadron electron Collider (LHeC) in the search for heavy neutral scalar particles. We consider a minimal model with one additional complex scalar singlet that interacts with the Standard Model (SM) via mixing with the Higgs doublet, giving rise to a SM-like Higgs boson $h_1$ and a heavy scalar particle $h_2$. Both scalar particles are produced via vector boson fusion and can be tested via their decays into pairs of SM particles, analogously to the SM Higgs boson. Using multivariate techniques we show that the LHeC is sensitive to $h_2…
We analyze the physics potential of long baseline neutrino oscillation experiments planned for the coming ten years, where the main focus is the sensitivity limit to the small mixing angle $θ_{13}$. The discussed experiments include the conventional beam experiments MINOS, ICARUS, and OPERA, which are under construction, the planned superbeam experiments J-PARC to Super-Kamiokande and NuMI off-axis, as well as new reactor experiments with near and far detectors, represented by the Double-Chooz project. We perform a complete numerical simulation including systematics, correlations, and degenera…
If dark matter has mass lower than around 1 GeV, it will not impart enough energy to cause detectable nuclear recoils in many direct-detection experiments. However, if dark matter is upscattered to high energy by collisions with cosmic rays, it may be detectable in both direct-detection experiments and neutrino experiments. We report the results of a dedicated search for boosted dark matter upscattered by cosmic rays using the PROSPECT reactor antineutrino experiment. We show that such a flux of upscattered dark matter would display characteristic diurnal sidereal modulation, and use this to s…
We explore the prospects of determining the octant of $θ_{23}$ with atmospheric neutrinos at PINGU. We study in detail the impact of energy and angle resolutions of the neutrino on the octant sensitivity. We show that the systematic uncertainties on the atmospheric neutrino flux predictions, especially the ones which affect the energy and zenith angle spectrum of the neutrinos, make a rather drastic reduction of the sensitivity of PINGU. We also study the prospects of measuring the octant of $θ_{23}$ in the long baseline experiments T2K and NOvA in conjunction with the reactor experiments. We …
New studies of the ATLAS and CMS collaborations are presented on the sensitivity to searches for non-standard signatures of particular SUSY scenarios. These signatures include non-pointing photons, as well as pairs of prompt photons, as expected in GMSB SUSY models, as well as heavy stable charged particles produced in split supersymmetry models, long lived staus from GMSB SUSY and long lived stops in other SUSY scenarios. A detailed detector simulation is used for the study, and all relevant Standard Model backgrounds and detector effects that can mimic these special signatures are included. …
I summarize the status of neutrino oscillations from world neutrino oscillation data with date of October 2005. The results of a global analysis within the three-flavour framework are presented. Furthermore, a prospect on where we could stand in neutrino oscillations in ten years from now is given, based on a simulation of upcoming long-baseline accelerator and reactor experiments.
After the observation of a Higgs boson near 125 GeV, the high energy physics community is investigating possible next steps for entering into a new era in particle physics. It is planned that the Large Hadron Collider will deliver an integrated luminosity of up to 3000/fb for the CMS and ATLAS experiments, requiring several upgrades for all detectors. The reach of various representative searches for supersymmetry and exotica physics with the upgraded detectors are discussed in this context, where a very high instantaneous luminosity will lead to a large number of pileup events in each bunch cr…
While most BSM searches at the LHC focus on heavy new states, the NMSSM contains the possibility of new light states that have escaped detection due to their singlet nature. Here we focus on light pseudoscalars, investigating the parameter space impact of recent LHC searches for such light states stemming from the decay of the 125 GeV Higgs boson. It is shown that, though direct searches can not yet compete with the requirement of the 125 GeV scalar having SM-like couplings, the searches are touching the allowed parameter space and should make a phenomenological impact in the near future.
We present a method how to detect the WH -> lnbb in the high luminosity LHC environment with the CMS detector. This study is performed with fast detector response simulation including high luminosity event pile up. The main aspects of reconstruction are pile up jet rejection, identification of b-jets and improvement of Higgs mass resolution. The detection potential in the SM for m(H) < 130 GeV and in the MSSM is only encouraging for high integrated luminosity. Nevertheless it is possible to extract important Higgs parameters which are useful to elucidate the nature of the Higgs sector. In comb…
Unlike the relic photons, relic neutrinos have not so far been observed. The Cosmic Neutrino Background (C$ν$B) is the oldest relic from the Big Bang, produced a few seconds after the Bang itself. Due to their impact in cosmology, relic neutrinos may be revealed indireclty in the near future through cosmological observations. In this talk we concentrate on other proposals, made in the last 30 years, to try to detect the C$ν$B directly, either in laboratory searches (through tiny accelerations they produce on macroscopic targets) or through astrophysical observations (looking for absorption dip…
Motivated by recent progress in experimental techniques of electric dipole moment (EDM) measurements, we study correlations between the neutron and electron EDMs in common supersymmetric models. These include minimal supergravity (mSUGRA) with small CP phases, mSUGRA with a heavy SUSY spectrum, the decoupling scenario and split SUSY. In most cases, the electron and neutron EDMs are found to be observable in the next round of EDM experiments. They exhibit certain correlation patterns. For example, if d_n ~ 10^{-27} e cm is found, d_e is predicted to lie in the range 10^{-28}-10^{-29} e cm.
We propose a search for direct production and decay of the lightest supersymmetric Higgs boson to two neutralinos in gauge mediated models at the Fermilab Tevatron. We focus on the final state where each neutralino decays to photon and light gravitino with a lifetime of order O(ns). In the detector this will show up as a photon with a time-delayed signature and missing E_T. We estimate that using the photon timing system at CDF, and the full 10/fb data sample, that the sensitivity can be within a factor of three in some regions of parameter space for direct production of the Higgs.
We report on the potential for the discovery of a Standard Model Higgs boson with the vector boson fusion mechanism in the mass range $115<M_H<500 \gev$ with the ATLAS experiment at the LHC. Feasibility studies at hadron level followed by a fast detector simulation have been performed for $H\to W^{(*)}W^{(*)}\to l^+l^-\sla{p_T}$, $H\toγγ$ and $H\to ZZ\to l^+l^-q\bar{q}$. The results obtained show a large discovery potential in the range $115<M_H<300 \gev$. Results obtained with multivariate techniques are reported for a number of channels.
Searches for mass-3 component in the electron neutrino flavor state $\sinθ_{13}$ and for sterile neutrinos can be carried out in the same small mixing angle antineutrino oscillation experiment at a reactor. As an example we consider a layout, which involves several movable antineutrino spectrometers, stationed at distances 1700 m $-$ 50 m from a reactor. The experiment can scan neutrino mass parameter interval $\sim$(0.5$-$0.001) eV$^{2}$ and have there typical sensitivity to $\sin^{2}2θ$ at a level of 0.015$-$0.02. The signature for sterile neutrino is disappearance observed at mass parameter…
In this addendum to arXiv:1103.0734 we consider the recent results from long-baseline $ν_μ\toν_e$ searches at the T2K and MINOS experiments and investigate their implications for the mixing angle $θ_{13}$ and the leptonic Dirac CP phase $δ$. By combining the $2.5σ$ indication for a non-zero value of $θ_{13}$ coming from T2K data with global neutrino oscillation data we obtain a significance for $θ_{13} > 0$ of about $3σ$ with best fit points $\sin^2θ_{13} = 0.013(0.016)$ for normal (inverted) neutrino mass ordering. These results depend somewhat on assumptions concerning the analysis of reacto…
We present the prospects of searches for neutral, long-lived particles which decay to photons using their time of arrival measured with a newly installed timing system on the electromagnetic calorimeter (EMTiming) of the Collider Detector at Fermilab (CDF). A Monte Carlo simulation shows that EMTiming can provide separation between decay photons from particles with both a long lifetime and a low boost, and prompt photons from Standard Model backgrounds. Using a gauge mediated supersymmetry breaking (GMSB) $\tildeχ_{1}^{0}\toγ\tilde{G}$ model we estimate a quasi-model-independent sensitivity us…
The neutrino oscillation probabilities in vacuum and matter are discussed, considering the framework of three active and one light sterile neutrinos. We study in detail the rephasing invariants and CP asymmetry observables, and investigate the four-neutrino oscillations in long-baseline neutrino experiments, such as DUNE, NO$ν$A and T2HK. Our results show that the matter effect enhances quite a significantly the oscillation probabilities of electron neutrino and electron antineutrino appearance channels within a certain energy range, while no considerable change arises in the CP asymmetry anal…
The type II seesaw mechanism is an attractive way to generate the observed light neutrino masses. It postulates a SU(2)$_\mathrm{L}$-triplet scalar field, which develops an induced vacuum expectation value after electroweak symmetry breaking, giving masses to the neutrinos via its couplings to the lepton SU(2)$_\mathrm{L}$-doublets. When the components of the triplet field have masses around the electroweak scale, the model features a rich phenomenology. We discuss the current allowed parameter space of the minimal low scale type II seesaw model, taking into account all relevant constraints, i…
We examine relation between neutrino oscillation parameters and prediction of lepton flavor violation, in light of deviations from tri-bimaximal mixing. Our study shows that upcoming experimental searches for lepton flavor violation process can provide useful implications for neutrino mass spectrum and mixing angles. With simple structure of heavy right-handed neutrino and supersymmetry breaking sectors, the discovery of tau \to mu gamma decay determines neutrino mass hierarchy if large (order 0.1) reactor angle is established.
Terrestrial Matter Effects on Reactor Antineutrino Oscillations: Constant vs. Fluctuated Density Profiles
Institute of High Energy Physics, Chinese Academy of Sciences（中国科学院高能物理研究所）；East China University of Technology（华东理工大学）；Institute of Geology and Geophysics, Chinese academy of sciences（中国科学院地质与地球物理研究所）；Institute of Modern Physics, Chinese Academy of Sciences（中国科学院近代物理研究所）；School of Physical Sciences, University of Chinese Academy of Sciences（中国科学院大学物理科学学院）
We compare the prospects for detecting a neutrino magnetic moment by the measurement of neutrinos from a tritium source, reactors and low-energy beta-beams. In all cases the neutrinos or antineutrinos are detected by scattering of electrons. We find that a large (20 MCurie) tritium source could improve the limit on the neutrino magnetic moment significantly, down to the level of a few $\times 10^{-12}$ while low-energy beta-beams with sufficiently rapid production of ions could improve the limits to the level of a few $\times 10^{-11}$. The latter would require ion production at the rate of at…
A considerable experimental effort is currently under way to test the persistent hints for oscillations due to an eV-scale sterile neutrino in the data of various reactor neutrino experiments. The assessment of the statistical significance of these hints is usually based on Wilks' theorem, whereby the assumption is made that the log-likelihood is $χ^2$-distributed. However, it is well known that the preconditions for the validity of Wilks' theorem are not fulfilled for neutrino oscillation experiments. In this work we derive a simple asymptotic form of the actual distribution of the log-likeli…
We reexamine the constrained version of the Next-to-Minimal Supersymmetric Standard Model with semi universal parameters at the GUT scale (CNMSSM). We include constraints from collider searches for Higgs and SUSY particles, upper bound on the relic density of dark matter, measurements of the muon anomalous magnetic moment and of B-physics observables as well as direct searches for dark matter. We then study the prospects for direct detection of dark matter in large scale detectors and comment on the prospects for discovery of heavy Higgs states at the LHC.
We investigate the prospects for the discovery of a neutral Higgs boson produced in association with a $b$ quark, followed by the Higgs decay into a pair of bottom quarks, $pp \to bϕ^0 \to b b\bar{b} +X$, at the CERN Large Hadron Collider (LHC) within the framework of unified supersymmetric models. The Higgs boson $ϕ^0$ can be a heavy scalar $H^0$ or a pseudoscalar $A^0$. Furthermore, this direct discovery channel is compared with the indirect Higgs searches in the rare decay $B_s \to μ^+μ^-$ at hadron colliders. Promising results are found for the minimal supergravity (mSUGRA) model, the anom…
We present projections for future collider searches for dark matter produced in association with bottom or top quarks. Such production channels give rise to final states with missing transverse energy and one or more b-jets. Limits are given assuming an effective scalar operator coupling dark matter to quarks, where the dedicated analysis discussed here improves significantly over a generic monojet analysis. We give updated results for an anticipated high-luminosity LHC run at 14 TeV and for a 33 TeV hadron collider.
