arXiv subjects

Surjeet Rajendran

Publications and source records attributed to Surjeet Rajendran.

At least 73 records · Page 4Linked to original sources

arXiv2021

Pathfinder for a High Statistics Search for Missing Energy In Gamma Cascades

We investigate the feasibility of a high statistics experiment to search for invisible decay modes in nuclear gamma cascades using 200 kg of %36 Cs(Tl) scintillators that are presently available at Texas A\&M. The experiment aims to search for missing energy by robustly establishing the absence of a photon in a well identified gamma cascade. We report on the experimental demonstration of the energy resolution necessary for this search. Prior explorations of this detector concept focused on baryonically coupled physics that could be emitted in $E_2$ transitions. We point out that this protocol can also search for particles that are coupled to photons by searching for the conversion of a photon produced in a gamma cascade into a hidden particle. Examples of these processes include the oscillation of a photon into a hidden photon and the conversion of a photon into an axion-like-particle either in the presence of a magnetic field or via the Primakoff process. This proof-of-concept apparatus appears to have the ability to search for hitherto unconstrained baryonically coupled scalars and pseudoscalars produced in $E_0$ and $M_0$ transitions. If successfully implemented, this experiment serves as a pathfinder for a larger detector with greater containment that can thoroughly probe the existence of new particles with mass below 4 MeV that lie in the poorly constrained supernova ``trapping window'' that exists between 100 keV and 30 MeV.

hep-ph↗

arXiv2021

The missing link in gravitational-wave astronomy: A summary of discoveries waiting in the decihertz range

Since 2015 the gravitational-wave observations of LIGO and Virgo have transformed our understanding of compact-object binaries. In the years to come, ground-based gravitational-wave observatories such as LIGO, Virgo, and their successors will increase in sensitivity, discovering thousands of stellar-mass binaries. In the 2030s, the space-based LISA will provide gravitational-wave observations of massive black holes binaries. Between the $\sim 10$-$10^3~\mathrm{Hz}$ band of ground-based observatories and the $\sim10^{-4}$-$10^{-1}~\mathrm{Hz}$ band of LISA lies the uncharted decihertz gravitational-wave band. We propose a Decihertz Observatory to study this frequency range, and to complement observations made by other detectors. Decihertz observatories are well suited to observation of intermediate-mass ($\sim10^2$-$10^4 M_\odot$) black holes; they will be able to detect stellar-mass binaries days to years before they merge, providing early warning of nearby binary neutron star mergers and measurements of the eccentricity of binary black holes, and they will enable new tests of general relativity and the Standard Model of particle physics. Here we summarise how a Decihertz Observatory could provide unique insights into how black holes form and evolve across cosmic time, improve prospects for both multimessenger astronomy and multiband gravitational-wave astronomy, and enable new probes of gravity, particle physics and cosmology.

gr-qc↗

arXiv2021

Matter-wave Atomic Gradiometer Interferometric Sensor (MAGIS-100)

MAGIS-100 is a next-generation quantum sensor under construction at Fermilab that aims to explore fundamental physics with atom interferometry over a 100-meter baseline. This novel detector will search for ultralight dark matter, test quantum mechanics in new regimes, and serve as a technology pathfinder for future gravitational wave detectors in a previously unexplored frequency band. It combines techniques demonstrated in state-of-the-art 10-meter-scale atom interferometers with the latest technological advances of the world's best atomic clocks. MAGIS-100 will provide a development platform for a future kilometer-scale detector that would be sufficiently sensitive to detect gravitational waves from known sources. Here we present the science case for the MAGIS concept, review the operating principles of the detector, describe the instrument design, and study the detector systematics.

physics.atom-ph↗

arXiv2021

Opportunities for DOE National Laboratory-led QuantISED Experiments

A subset of QuantISED Sensor PIs met virtually on May 26, 2020 to discuss a response to a charge by the DOE Office of High Energy Physics. In this document, we summarize the QuantISED sensor community discussion, including a consideration of HEP science enabled by quantum sensors, describing the distinction between Quantum 1.0 and Quantum 2.0, and discussing synergies/complementarity with the new DOE NQI centers and with research supported by other SC offices. Quantum 2.0 advances in sensor technology offer many opportunities and new approaches for HEP experiments. The DOE HEP QuantISED program could support a portfolio of small experiments based on these advances. QuantISED experiments could use sensor technologies that exemplify Quantum 2.0 breakthroughs. They would strive to achieve new HEP science results, while possibly spinning off other domain science applications or serving as pathfinders for future HEP science targets. QuantISED experiments should be led by a DOE laboratory, to take advantage of laboratory technical resources, infrastructure, and expertise in the safe and efficient construction, operation, and review of experiments. The QuantISED PIs emphasized that the quest for HEP science results under the QuantISED program is distinct from the ongoing DOE HEP programs on the energy, intensity, and cosmic frontiers. There is robust evidence for the existence of particles and phenomena beyond the Standard Model, including dark matter, dark energy, quantum gravity, and new physics responsible for neutrino masses, cosmic inflation, and the cosmic preference for matter over antimatter. Where is this physics and how do we find it? The QuantISED program can exploit new capabilities provided by quantum technology to probe these kinds of science questions in new ways and over a broader range of science parameters than can be achieved with conventional techniques.

physics.ins-det↗

arXiv2021

Storage Ring Probes of Dark Matter and Dark Energy

We show that proton storage ring experiments designed to search for proton electric dipole moments can also be used to look for the nearly dc spin precession induced by dark energy and ultra-light dark matter. These experiments are sensitive to both axion-like and vector fields. Current technology permits probes of these phenomena up to three orders of magnitude beyond astrophysical limits. The relativistic boost of the protons in these rings allows this scheme to have sensitivities comparable to atomic co-magnetometer experiments that can also probe similar phenomena. These complementary approaches can be used to extract the micro-physics of a signal, allowing us to distinguish between pseudo-scalar, magnetic and electric dipole moment interactions.

hep-ph↗

arXiv2021

Search for axion-like dark matter using solid-state nuclear magnetic resonance

We report the results of an experimental search for ultralight axion-like dark matter in the mass range 162 neV to 166 neV. The detection scheme of our Cosmic Axion Spin Precession Experiment (CASPEr) is based on a precision measurement of $^{207}$Pb solid-state nuclear magnetic resonance in a polarized ferroelectric crystal. Axion-like dark matter can exert an oscillating torque on $^{207}$Pb nuclear spins via the electric-dipole moment coupling $g_d$, or via the gradient coupling $g_{\text{aNN}}$. We calibrated the detector and characterized the excitation spectrum and relaxation parameters of the nuclear spin ensemble with pulsed magnetic resonance measurements in a 4.4 T magnetic field. We swept the magnetic field near this value and searched for axion-like dark matter with Compton frequency within a 1 MHz band centered at 39.65 MHz. Our measurements place the upper bounds $|g_d|<9.5\times10^{-4}\,\text{GeV}^{-2}$ and $|g_{\text{aNN}}|<2.8\times10^{-1}\,\text{GeV}^{-1}$ (95% confidence level) in this frequency range. The constraint on $g_d$ corresponds to an upper bound of $1.0\times 10^{-21}\,\text{e}\cdot\text{cm}$ on the amplitude of oscillations of the neutron electric dipole moment, and $4.3\times 10^{-6}$ on the amplitude of oscillations of CP-violating $θ$ parameter of quantum chromodynamics. Our results demonstrate the feasibility of using solid-state nuclear magnetic resonance to search for axion-like dark matter in the nano-electronvolt mass range.

hep-ex↗

arXiv2020

Dark Energy Radiation

We show that if dark energy evolves in time, its dynamical component could be dominated by a bath of dark radiation. Within current constraints this radiation could have up to $\sim 10^4$ times more energy density than the cosmic microwave background. We demonstrate particular models in which a rolling scalar field generates different forms of dark radiation such as hidden photons, milli-charged particles and even Standard Model neutrinos. We find the leading effect on the late-time cosmological expansion history depends on a single parameter beyond $Λ$CDM, namely the temperature of the dark radiation today. Cosmological observations of this modified expansion rate could provide a striking signature of this scenario. The dark radiation itself could even be directly detectable in laboratory experiments, suggesting a broader experimental program into the nature of dark energy.

hep-ph↗

arXiv2020

Exploring the robustness of stellar cooling constraints on light particles

Stellar cooling arguments place strict restrictions on a wide variety of models of new physics. In this paper, we argue that mechanisms to evade these constraints are restricted by thermodynamic arguments, then present a minimal model extension that allows new particles to evade all stellar constraints. In doing this, we demonstrate that interesting parameter space can be reopened, using the EDGES signal and Xenon1T excess as examples. This mechanism highlights the importance of laboratory experiments in a well-controlled environment to search for new physics, complementary to astrophysical searches.

hep-ph↗

arXiv2020

Searching for New Interactions at Sub-micron Scale Using the Mossbauer Effect

A new technique to search for new scalar and tensor interactions at the sub-micrometer scale is presented. The technique relies on small shifts of nuclear gamma lines produced by the coupling between matter and the nuclei in the source or absorber of a Mossbauer spectrometer. Remarkably, such energy shifts are rather insensitive to electromagnetic interactions that represent the largest background in searches for new forces using atomic matter. This is because nuclei are intrinsically shielded by the electron clouds. Additionally, electromagnetic interactions cause energy shifts by coupling to nuclear moments that are suppressed by the size of the nuclei, while new scalar interactions can directly affect these shifts. Finally, averaging over unpolarized nuclei, further reduces electromagnetic interactions. We discuss several possible configurations, using the traditional Mossbauer effect as well as nuclear resonant absorption driven by synchrotron radiation. For this purpose, we examine the viability of well known Mossbauer nuclides along with more exotic ones that result in substantially narrower resonances. We find that the technique introduced here could substantially improve the sensitivity to a variety of new interactions and could also be used, in conjunction with mechanical force measurements, to corroborate a discovery or explore the new physics that may be behind a discovery.

hep-ph↗

arXiv2020

A Composite Solution to the Neutron Bottle Anomaly

Measurements of the lifetime of neutrons trapped in a bottle have been consistently shorter than the lifetime measured in neutron beam experiments. With trapping potentials as low as 50 neV and neutron detectors located only at the top of the bottle, this discrepancy could be the result of the soft scattering of dark matter with neutrons. However, it is challenging to obtain the observed loss rate in conventional models of dark matter scattering. We show that this phenomenology is possible in composite models of dark matter where the soft scattering is from dark matter that has been captured and accumulated in the earth. This solution can be tested by placing more neutron detectors around the trap, providing better angular coverage. The phenomenology of soft scattering by trapped composite dark matter is generic and suggests new experimental directions that could be pursued to detect this large class of models.

hep-ph↗

arXiv2020

Quasinormal Modes and Stability of Firewalls

A solution to the black hole information problem requires propagation of information from the interior of the black hole to the exterior. Such propagation violates general relativity and could conceivably be accomplished through "firewall" models. Based on the existence of similar firewalls at the inner horizons of charged and rotating black holes, a model of a firewall was recently constructed where the exterior spacetime reduces to that of the Schwarzschild metric but with a dramatically different interior. We investigate the radial and nonradial polar stability of these objects. We first study the dynamics of the shell under spherically symmetric perturbations, and impose constraints on the firewall model parameters by requiring a subluminal speed of sound on the firewall. We show that the demands of stability and subluminality impose significant constraints on the internal parameters of the firewall, narrowing down the range of objects that could be used to create such a structure.

gr-qc↗

arXiv2020

The Missing Link in Gravitational-Wave Astronomy: Discoveries waiting in the decihertz range

The gravitational-wave astronomical revolution began in 2015 with LIGO's observation of the coalescence of two stellar-mass black holes. Over the coming decades, ground-based detectors like LIGO will extend their reach, discovering thousands of stellar-mass binaries. In the 2030s, the space-based LISA will enable gravitational-wave observations of the massive black holes in galactic centres. Between LISA and ground-based observatories lies the unexplored decihertz gravitational-wave frequency band. Here, we propose a Decihertz Observatory to cover this band, and complement observations made by other gravitational-wave observatories. The decihertz band is uniquely suited to observation of intermediate-mass ($\sim 10^2$-$10^4 M_\odot$) black holes, which may form the missing link between stellar-mass and massive black holes, offering a unique opportunity to measure their properties. Decihertz observations will be able to detect stellar-mass binaries days to years before they merge and are observed by ground-based detectors, providing early warning of nearby binary neutron star mergers, and enabling measurements of the eccentricity of binary black holes, providing revealing insights into their formation. Observing decihertz gravitational-waves also opens the possibility of testing fundamental physics in a new laboratory, permitting unique tests of general relativity and the Standard Model of particle physics. Overall, a Decihertz Observatory will answer key questions about how black holes form and evolve across cosmic time, open new avenues for multimessenger astronomy, and advance our understanding of gravitation, particle physics and cosmology.

gr-qc↗

arXiv2020

High-Frequency Gravitational-Wave Detection Using a Chiral Resonant Mechanical Element and a Short Unstable Optical Cavity

Present gravitational wave detectors are based on the measurement of linear displacement in stable optical cavities. Here, we instead suggest the measurement of the twist of a chiral mechanical element induced by a gravitational wave. The induced twist rotates a flat optical mirror on top of this chiral element, leading to the deflection of an incident laser beam. This angle change is enhanced by multiple bounces of light between the rotating mirror and an originally parallel nearby fixed flat mirror. Based on detailed continuum-mechanics calculations, we present a feasible design for the chiral mechanical element including the rotating mirror. Our approach is most useful for signals in the frequency band 1 -- 100 kHz where we show that fundamental metrological limits would allow for smaller shot noise in this setup in comparison to the detection of linear displacement. We estimate a gravitational wave strain sensitivity between 10^{-21}/\sqrt{Hz} and 10^{-23}/\sqrt{Hz} at around 10 kHz frequency. When appropriately scaling the involved geometrical parameters, the strain sensitivity is proportional to frequency.

gr-qc↗

arXiv2020

Metastable Nuclear Isomers as Dark Matter Accelerators

Inelastic dark matter and strongly interacting dark matter are poorly constrained by direct detection experiments since they both require the scattering event to deliver energy from the nucleus into the dark matter in order to have observable effects. We propose to test these scenarios by searching for the collisional de-excitation of meta-stable nuclear isomers by the dark matter particles. The longevity of these isomers is related to a strong suppression of $γ$- and $β$-transitions, typically inhibited by a large difference in the angular momentum for the nuclear transition. The collisional de-excitation by dark matter is possible since heavy dark matter particles can have a momentum exchange with the nucleus comparable to the inverse nuclear size, hence lifting tremendous angular momentum suppression of the nuclear transition. This de-excitation can be observed either by searching for the direct effects of the decaying isomer, or through the re-scattering or decay of excited dark matter states in a nearby conventional dark matter detector setup. Existing nuclear isomer sources such as naturally occurring $^{180m}$Ta, $^{137m}$Ba produced in decaying Cesium in nuclear waste, $^{177m}$Lu from medical waste, and $^{178m}$Hf from the Department of Energy storage can be combined with current dark matter detector technology to search for this class of dark matter.

hep-ph↗

arXiv2020

Observable signatures of dark photons from supernovae

A dark photon is a well-motivated new particle which, as a component of an associated dark sector, could explain dark matter. One strong limit on dark photons arises from excessive cooling of supernovae. We point out that even at couplings where too few dark photons are produced in supernovae to violate the cooling bound, they can be observed directly through their decays. Supernovae produce dark photons which decay to positrons, giving a signal in the 511 keV annihilation line observed by SPI/INTEGRAL. Further, prompt gamma-ray emission by these decaying dark photons gives a signal for gamma-ray telescopes. Existing GRS observations of SN1987a already constrain this, and a future nearby SN could provide a detection. Finally, dark photon decays from extragalactic SN would produce a diffuse flux of gamma rays observable by detectors such as SMM and HEAO-1. Together these observations can probe dark photon couplings several orders of magnitude beyond current constraints for masses of roughly 1 - 100 MeV.

hep-ph↗

arXiv2020

White Dwarf Bounds on CHAMPs

White dwarfs (WD) effectively act as high-gain amplifiers for relatively small energy deposits within their volume via their supernova instability. In this paper, we consider the ways a galactic abundance of $\mathcal{O}(1)$-charged massive relics (i.e., CHAMPs) could trigger this instability, thereby destroying old WD. The dense central core structure formed inside the WD when heavy CHAMPs sink to its center can trigger a supernova via injection of energy during collapse phases, via direct density-enhanced (pycnonuclear) fusion processes of carbon nuclei dragged into the core by the CHAMPs, or via the formation of a black hole (BH) at the center of the WD. In the latter scenario, Hawking radiation from the BH can ignite the star if the BH forms with a sufficiently small mass; if the BH instead forms at large enough mass, heating of carbon nuclei that accrete onto the BH as it grows in size may be able to achieve the same outcome (with the conservative alternative being simply that the WD is devoured by the BH). The known existence of old WD that have not been destroyed by these mechanisms allows us to improve by many orders of magnitude on the existing CHAMP abundance constraints in the regime of large CHAMP mass, $m_X \sim 10^{11}$-$10^{18}\,$GeV. Additionally, in certain regions of parameter space, we speculate that this setup could provide a trigger mechanism for the calcium-rich gap transients: a class of anomalous, sub-luminous supernova events that occur far outside of a host galaxy.

hep-ph↗

arXiv2020

Quantum Detection using Magnetic Avalanches in Single-Molecule Magnets

The detection of a single quantum of energy with high efficiency and low false positive rate is of considerable scientific interest, from serving as single quantum sensors of optical and infra-red photons to enabling the direct detection of low-mass dark matter. We report the first experimental demonstration of magnetic avalanches induced by scattering of quanta in single-molecule magnet (SMM) crystals made of Mn12-acetate, establishing the use of SMMs as particle detectors for the first time. While the current setup has an energy threshold in the MeV regime, our results motivate the exploration of a wide variety of SMMs whose properties could allow for detection of sub-eV energy depositions.

physics.ins-det↗

arXiv2020

Clocking Out Superradiance Limits

The superradiant instability of black hole space-times has been used to place limits on ultra-light bosonic particles. We show that these limits are model dependent. While the initial growth of the mode is gravitational and thus model independent, the ability to place a limit on new particles requires the mode to grow unhindered to a large number density. Non-linear interactions between the particle and other light degrees of freedom that are mediated through higher dimension operators can damp this growth, eliminating the limit. However, these non-linearities may also destroy a cosmic abundance of these light particles, an attractive avenue for their discovery in several experiments. We study the specific example of the QCD axion and show that it is easy to construct models where these non-linearities eliminate limits from superradiance while preserving their cosmic abundance.

hep-ph↗