arXiv subjects

David G. Cerdeno

Publications and source records attributed to David G. Cerdeno.

At least 19 recordsLinked to original sources

arXiv2021

Light new physics in XENON1T

We examine the recently-reported low-energy electron recoil spectrum observed at the XENON1T underground dark matter direct detection experiment, in the context of new interactions with solar neutrinos. In particular we show that scalar and vector mediators with masses $\lesssim 50$ keV coupled to leptons could already leave a visible signature in the XENON1T experiment, similar to the observed peak below 7 keV. This signals that dark matter detectors are already competing with neutrino scattering experiments such as GEMMA, CHARM-II and Borexino. If these results from XENON1T are interpreted as a new signal of such physics, the parameters which fit the excess face challenges from astrophysics which seem very difficult to overcome. If they are rather viewed as a constraint on new couplings, they herald the start of an era of novel precise probes of physics beyond the standard model with dark matter detectors.

hep-ph↗

arXiv2021

Solar neutrino probes of the muon anomalous magnetic moment in the gauged $U(1)_{L_μ-L_τ}$

Models of gauged $U(1)_{L_μ-L_τ}$ can provide a solution to the long-standing discrepancy between the theoretical prediction for the muon anomalous magnetic moment and its measured value. The extra contribution is due to a new light vector mediator, which also helps to alleviate an existing tension in the determination of the Hubble parameter. In this article, we explore ways to probe this solution via the scattering of solar neutrinos with electrons and nuclei in a range of experiments and considering high and low solar metallicity scenarios. In particular, we reevaluate Borexino constraints on neutrino-electron scattering, finding them to be more stringent than previously reported, and already excluding a part of the $(g-2)_μ$ explanation with mediator masses smaller than $2\times10^{-2}$ GeV. We then show that future direct dark matter detectors will be able to probe most of the remaining solution. Due to its large exposure, LUX-ZEPLIN will explore regions with mediator masses up to $5\times10^{-2}$ GeV and DARWIN will be able to extend the search beyond $10^{-1}$ GeV, thereby covering most of the area compatible with $(g-2)_μ$. For completeness, we have also computed the constraints derived from the recent XENON1T electron recoil search and from the CENNS-10 LAr detector, showing that none of them excludes new areas of the parameter space. Should the excess in the muon anomalous magnetic moment be confirmed, our work suggests that direct detection experiments could provide crucial information with which to test the $U(1)_{L_μ-L_τ}$ solution, complementary to efforts in neutrino experiments and accelerators.

hep-ph↗

arXiv2020

The dark matter component of the Gaia radially anisotropic substructure

We study the properties of the dark matter component of the radially anisotropic stellar population recently identified in the Gaia data, using magneto-hydrodynamical simulations of Milky Way-like halos from the Auriga project. We identify 10 simulated galaxies that approximately match the rotation curve and stellar mass of the Milky Way. Four of these have an anisotropic stellar population reminiscent of the Gaia structure. We find an anti-correlation between the dark matter mass fraction of this population in the Solar neighbourhood and its orbital anisotropy. We estimate the local dark matter density and velocity distribution for halos with and without the anisotropic stellar population, and use them to simulate the signals expected in future xenon and germanium direct detection experiments. We find that a generalized Maxwellian distribution fits the dark matter halo integrals of the Milky Way-like halos containing the radially anisotropic stellar population. For dark matter particle masses below approximately 10 GeV, direct detection exclusion limits for the simulated halos with the anisotropic stellar population show a mild shift towards smaller masses compared to the commonly adopted Standard Halo Model.

astro-ph.GA↗

arXiv2019

Impact of new physics on $B+L$ violation at colliders

In the Standard Model, chiral electroweak anomalies predict nonperturbative interactions that violate baryon ($B$) plus lepton number ($L$). The potential observability of these processes at colliders has been amply discussed in the literature, mostly focusing on the impact of the accompanying boson emission, which contributes to the cross sections through an exponential function of the center-of-mass energy. We focus instead on the impact of exotic fermions charged under $SU(2)_L$, which not only can be emitted in these processes, but also affect the non-exponential contributions to the cross-sections. Estimating the latter using instanton techniques, we find sizable effects that suggest that if $B+L$-violating processes are ever seen at colliders, they may involve physics beyond the Standard Model.

hep-ph↗

arXiv2019

On the correlation between the local dark matter and stellar velocities

The dark matter velocity distribution in the Solar neighbourhood is an important astrophysical input which enters in the predicted event rate of dark matter direct detection experiments. It has been recently suggested that the local dark matter velocity distribution can be inferred from that of old or metal-poor stars in the Milky Way. We investigate this potential relation using six high resolution magneto-hydrodynamical simulations of Milky Way-like galaxies of the Auriga project. We do not find any correlation between the velocity distributions of dark matter and old stars in the Solar neighbourhood. Likewise, there are no strong correlations between the local velocity distributions of dark matter and metal-poor stars selected by applying reasonable cuts on metallicity. In some simulated galaxies, extremely metal-poor stars have a velocity distribution that is statistically consistent with that of the dark matter, but the sample of such stars is so small that we cannot draw any strong conclusions.

astro-ph.GA↗

arXiv2018

Opening the energy window on direct dark matter detection

In this article we investigate the benefits of increasing the maximum nuclear recoil energy analysed in dark matter (DM) direct detection experiments. We focus on elastic DM-nucleus interactions, and work within the framework of effective field theory (EFT) to describe the scattering cross section. In agreement with previous literature, we show that an increased maximum energy leads to more stringent upper bounds on the DM-nucleus cross section for the EFT operators, especially those with an explicit momentum dependence. In this article we extend the energy region of interest (ROI) to show that the optimal values of the maximum energy for xenon and argon are of the order of 500 keV and 300 keV, respectively. We then show how, if a signal compatible with DM is observed, an enlarged energy ROI leads to a better measurement of the DM mass and couplings. In particular, for a xenon detector, DM masses of the order of 200 GeV (2 TeV) or lower can be reconstructed for momentum-independent (-dependent) operators. We also investigate three-dimensional parameter reconstruction and apply it to the specific case of scalar DM and anapole DM. We find that opening the energy ROI is an excellent way to identify the linear combination of momentum-dependent and momentum-independent operators, and it is crucial to correctly distinguish these models. Finally, we show how an enlarged energy ROI also allows us to test astrophysical parameters of the DM halo, such as the DM escape speed.

hep-ph↗

arXiv2018

The Power of Genetic Algorithms: what remains of the pMSSM?

Genetic Algorithms (GAs) are explored as a tool for probing new physics with high dimensionality. We study the 19-dimensional pMSSM, including experimental constraints from all sources and assessing the consistency of potential signals of new physics. We show that GAs excel at making a fast and accurate diagnosis of the cross-compatibility of a set of experimental constraints in such high dimensional models. In the case of the pMSSM, it is found that only ${\cal O}(10^4)$ model evaluations are required to obtain a best fit point in agreement with much more costly MCMC scans. This efficiency allows higher dimensional models to be falsified, and patterns in the spectrum identified, orders of magnitude more quickly. As examples of falsification, we consider the muon anomalous magnetic moment, and the Galactic Centre gamma-ray excess observed by Fermi-LAT, which could in principle be explained in terms of neutralino dark matter. We show that both observables cannot be explained within the pMSSM, and that they provide the leading contribution to the total goodness of the fit, with $χ^2_{δa_μ^{\mathrm{SUSY}}}\approx12$ and $χ^2_{\rm GCE}\approx 155$, respectively.

hep-ph↗

arXiv2018

$B+L$ violation at colliders and new physics

Chiral electroweak anomalies predict fermion interactions that violate baryon ($B$) and lepton number ($L$), and can be dressed with large numbers of Higgs and gauge bosons. The estimation of the total $B+L$ violating rate from an initial two-particle state --potentially observable at colliders-- has been the subject of an intense discussion, mainly centered on the resummation of boson emission, which is believed to contribute to the cross-section with an exponential function of the energy, yet with an exponent (the "holy-grail" function) which is not fully known in the energy range of interest. In this article we focus instead on the effect of fermions beyond the Standard-Model (SM) in the polynomial contributions to the rate. It is shown that $B+L$ processes involving the new fermions have a polynomial contribution that can be several orders of magnitude greater than in the SM, for high centre-of-mass energies and light enough masses. We also present calculations that hint at a simple dependence of the holy grail function on the heavy fermion masses. Thus, if anomalous $B+L$ violating interactions are ever detected at high-energy colliders, they could be associated with new physics.

hep-ph↗

arXiv2018

CNO Neutrino Grand Prix: The race to solve the solar metallicity problem

Several next-generation experiments aim to make the first measurement of the neutrino flux from the Carbon-Nitrogen-Oxygen (CNO) solar fusion cycle. We calculate how much time these experiments will need to run for in order to measure this flux with enough precision to tell us the metal content of the Sun's core, and thereby help to solve the solar metallicity problem. For experiments looking at neutrino-electron scattering, we find that SNO+ will measure this CNO neutrino flux with enough precision after five years in its pure scintillator mode, provided its $^{210}$Bi background is measured to 1% accuracy. By comparison, a 100~ton liquid argon experiment such as Argo will take ten years in Gran Sasso lab, or five years in SNOLAB or Jinping. Borexino could obtain this precision in ten years, but this projection is very sensitive to background assumptions. For experiments looking at neutrino-nucleus scattering, the best prospects are obtained for low-threshold solid state detectors (employing either germanium or silicon). These would require new technologies to lower the experimental threshold close to detection of single electron-hole pairs, and exposures beyond those projected for next-generation dark matter detectors.

hep-ph↗

arXiv2017

The Constrained NMSSM with right-handed neutrinos

In this article, we study the renormalization group equations of the Next-to-Minimal Supersymmetric Standard Model, and investigate universality conditions on the soft supersymmetry-breaking parameters at the Grand Unification scale. We demonstrate that the inclusion of right-handed neutrino superfields can have a substantial effect on the running of the soft terms (greatly contributing to driving the singlet Higgs mass- squared parameter negative), which makes it considerably easier to satisfy the conditions for radiative electroweak symmetry-breaking. The new fields also lead to larger values of the Standard Model Higgs mass, thus making it easier to reproduce the measured value. We investigate the phenomenology of this constrained scenario, and focus on two viable benchmark points, which feature a neutral lightest supersymmetric particle (either the lightest neutralino or the right-handed sneutrino). We show that all bounds from colliders and low-energy observables can be fulfilled in wide areas of the parameter space. However, the relic density in these regions is generally too high requiring some form of late entropy production to dilute the density of the lightest supersymmetric particle.

hep-ph↗

arXiv2017

Towards the next generation of simplified Dark Matter models

This White Paper is an input to the ongoing discussion about the extension and refinement of simplified Dark Matter (DM) models. Based on two concrete examples, we show how existing simplified DM models (SDMM) can be extended to provide a more accurate and comprehensive framework to interpret and characterise collider searches. In the first example we extend the canonical SDMM with a scalar mediator to include mixing with the Higgs boson. We show that this approach not only provides a better description of the underlying kinematic properties that a complete model would possess, but also offers the option of using this more realistic class of scalar mixing models to compare and combine consistently searches based on different experimental signatures. The second example outlines how a new physics signal observed in a visible channel can be connected to DM by extending a simplified model including effective couplings. This discovery scenario uses the recently observed excess in the high-mass diphoton searches of ATLAS and CMS for a case study to show that such a pragmatic approach can aid the experimental search programme to verify/falsify a potential signal and to study its underlying nature. In the next part of the White Paper we outline other interesting options for SDMM that could be studied in more detail in the future. Finally, we discuss important aspects of supersymmetric models for DM and how these could help to develop of more complete SDMM.

hep-ex↗

arXiv2016

Physics from solar neutrinos in dark matter direct detection experiments

The next generation of dark matter direct detection experiments will be sensitive to both coherent neutrino-nucleus and neutrino-electron scattering. This will enable them to explore aspects of solar physics, perform the lowest energy measurement of the weak angle to date, and probe contributions from new theories with light mediators. In this article, we compute the projected nuclear and electron recoil rates expected in several dark matter direct detection experiments due to solar neutrinos, and use these estimates to quantify errors on future measurements of the neutrino fluxes, weak mixing angle and solar observables, as well as to constrain new physics in the neutrino sector. Our analysis shows that the combined rates of solar neutrino events in second generation experiments (SuperCDMS and LZ) can yield a measurement of the $pp$ flux to 2.5% accuracy via electron recoil, and slightly improve the $^8$B flux determination. Assuming a low-mass argon phase, projected tonne-scale experiments like DARWIN can reduce the uncertainty on both the $pp$ and boron-8 neutrino fluxes to below 1%. Finally, we use current results from LUX, SuperCDMS and CDMSlite to set bounds on new interactions between neutrinos and electrons or nuclei, and show that future direct detection experiments can be used to set complementary constraints on the parameter space associated with light mediators.

hep-ph↗

arXiv2016

How to calculate dark matter direct detection exclusion limits that are consistent with gamma rays from annihilation in the Milky Way halo

When comparing constraints on the Weakly Interacting Massive Particle (WIMP) properties from direct and indirect detection experiments it is crucial that the assumptions made about the dark matter (DM) distribution are realistic and consistent. For instance, if the Fermi-LAT Galactic centre GeV gamma-ray excess was due to WIMP annihilation, its morphology would be incompatible with the Standard Halo Model that is usually used to interpret data from direct detection experiments. In this article, we calculate exclusion limits from direct detection experiments using self-consistent velocity distributions, derived from mass models of the Milky Way where the DM halo has a generalized NFW profile. We use two different methods to make the mass model compatible with a DM interpretation of the Galactic centre gamma-ray excess. Firstly, we fix the inner slope of the DM density profile to the value that best fits the morphology of the excess. Secondly, we allow the inner slope to vary and include the morphology of the excess in the data sets used to constrain the gravitational potential of the Milky Way. The resulting direct detection limits differ significantly from those derived using the Standard Halo Model, in particular for light WIMPs, due to the differences in both the local DM density and velocity distribution.

astro-ph.CO↗

arXiv2014

Displaced vertices and long-lived charged particles in the NMSSM with right-handed sneutrinos

We study LHC signatures of displaced vertices and long-lived charged particles within the context of the Next-to-Minimal Supersymmetric Standard Model with right-handed (RH) sneutrinos. In this construction the RH neutrino can be produced directly from Higgs decays or in association with a RH sneutrino when the latter is the lightest supersymmetric particle. The RH neutrino is generally long-lived, since its decay width is proportional to the neutrino Yukawa, a parameter which is predicted to be small. The RH neutrino late decay can therefore give rise to displaced vertices at the LHC, which can be identified through the decay products, which involve two leptons (2l+ MET) or a lepton with two jets (ljj). We simulate this signal for the current LHC configuration (a centre of mass of 8 TeV and an integrated luminosity of L=20 fb^-1), and a future one (13 TeV and L=100 fb^-1). We show that a region of the parameter space of this model can be probed and that the RH neutrino mass can be reconstructed from the end-point of the two-lepton invariant mass distribution or the central value of the mass distribution for two jets plus one lepton. Another exotic signature of this construction is the production of a long-lived stau. If the stau is the next-to-lightest supersymmetric particle, it can decay through diagrams involving the small neutrino Yukawa, and would escape the detector leaving a characteristic trail. We also simulate this signal for various benchmark points and show that the model can be within the reach of the future run of the LHC.

hep-ph↗

arXiv2014

Collider signatures of a light NMSSM pseudoscalar in neutralino decays in the light of LHC results

We investigate signatures induced by a very light pseudoscalar Higgs in neutralino decays in the Next-to-Minimal Supersymmetric Standard Model (NMSSM) and determine their observability at the LHC. We concentrate on scenarios which feature two light scalar Higgs bosons (one of them is SM-like with a mass of 125 GeV and a singlet-like lighter one) with a very light (singlet-like) pseudoscalar Higgs in the mass range 2m_tau < m_a1 < 2m_b. We consider neutralino-chargino pair production and the subsequent decay X_{2,3}-> X_1 a1, which leads to topologies involving multi-leptons and missing transverse energy. We determine a set of selection cuts that can effectively isolate the signal from backgrounds of the Standard Model or the Minimal Supersymmetric Standard Model. We also exemplify the procedure with a set of benchmark points, for which we compute the expected number of events and signal strength for LHC with 8 TeV center of mass energy. We show that this signal can already be probed for some points in the NMSSM parameter space.

hep-ph↗

arXiv2013

Constraints on WIMP Annihilation for Contracted Dark Matter in the Inner Galaxy with the Fermi-LAT

We derive constraints on parameters of generic dark matter candidates by comparing theoretical predictions with the gamma-ray emission observed by the Fermi-LAT from the region around the Galactic Center. Our analysis is conservative since it simply requires that the expected dark matter signal does not exceed the observed emission. The constraints obtained in the likely case that the collapse of baryons to the Galactic Center is accompanied by the contraction of the dark matter are strong. In particular, we find that for bb and τ+τ- or W+W- dark matter annihilation channels, the upper limits on the annihilation cross section imply that the thermal cross section is excluded for a Weakly Interacting Massive Particle (WIMP) mass smaller than about 700 and 500 GeV, respectively. For the μ+ μ- channel, where the effect of the inverse Compton scattering is important, depending on models of the Galactic magnetic field the exclusion of the thermal cross-section is for a WIMP mass smaller than about 150 to 400 GeV. The upper limits on the annihilation cross section of dark matter particles obtained are two orders of magnitude stronger than without contraction. In the latter case our results are compatible with the upper limits from the Galactic halo analysis reported by the Fermi-LAT collaboration for the case in which the same conservative approach without modeling of the astrophysical background is employed.

astro-ph.HE↗

arXiv2013

Probing the two light Higgs scenario in the NMSSM with a low-mass pseudoscalar

In this article we propose a simultaneous collider search strategy for a pair of scalar bosons in the NMSSM through the decays of a very light pseudoscalar. The massive scalar has a mass around 126 GeV while the lighter one can have a mass in the vicinity of 98 GeV (thus explaining an apparent LEP excess) or be much lighter. The successive decay of this scalar pair into two light pseudoscalars, followed by leptonic pseudoscalar decays, produces clean multi-lepton final states with small or no missing energy. Furthermore, this analysis offers an alternate leptonic probe for the 126 GeV scalar that can be comparable with the ZZ* search channel. We emphasize that a dedicated experimental search for multi-lepton final states can be an useful probe for this scenario and, in general, for the NMSSM Higgs sector. We illustrate our analysis with two representative benchmark points and show how the LHC configuration with 8 TeV center-of-mass energy and 25 inverse femtobarns of integrated luminosity can start testing this scenario, providing a good determination of the light pseudoscalar mass and a relatively good estimation of the lightest scalar mass.

hep-ph↗

arXiv2012

Nuclear uncertainties in the spin-dependent structure functions for direct dark matter detection

We study the effect that uncertainties in the nuclear spin-dependent structure functions have in the determination of the dark matter (DM) parameters in a direct detection experiment. We show that different nuclear models that describe the spin-dependent structure function of specific target nuclei can lead to variations in the reconstructed values of the DM mass and scattering cross-section. We propose a parametrization of the spin structure functions that allows us to treat these uncertainties as variations of three parameters, with a central value and deviation that depend on the specific nucleus. The method is illustrated for germanium and xenon detectors with an exposure of 300 kg yr, assuming a hypothetical detection of DM and studying a series of benchmark points for the DM properties. We find that the effect of these uncertainties can be similar in amplitude to that of astrophysical uncertainties, especially in those cases where the spin-dependent contribution to the elastic scattering cross-section is sizable.

hep-ph↗