<p>ATOMKI nuclear anomaly has suggested a new BSM (beyond the standard model) boson with mass <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mo>∼</mo><mn>17</mn><mtext> </mtext><mtext> </mtext><mi>MeV</mi></mrow></math> emitted from excited nuclei and quickly decays into a pair of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>e</mi><mo>+</mo></msup><msup><mi>e</mi><mo>−</mo></msup></math>. In order to search for the new particle, we propose a new approach that utilizes the ongoing coherent CAPTAIN-Mills (CCM) ten-ton LAr (liquid argon) detectors. The neutrons from the Lujan target can scatter inelastically, but the PMT glass in the CCM detector can produce the new boson which solves the ATOMKI anomaly. The new boson can be detected from its decay to a <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>e</mi><mo>+</mo></msup><msup><mi>e</mi><mo>−</mo></msup></math> pair. We find that CCM probes a large area of the anomaly-allowable parameter space. We also show the prediction for a 100-ton LAr detector and five-ton EOS water detector.</p>

United States

Bhaskar Dutta

Bai-Shan Hu

Wei-Chih Huang

Richard G. Van de Water

Novel Approach to Investigate ATOMKI Anomaly Using Coherent CAPTAIN-Mills Detectors

The recent observation of global spin polarization of $$\Lambda $$ ( $$\bar{\Lambda }$$ ) hyperons and the spin alignment of $$\phi $$ and $$K^{*0}$$ vector mesons create remarkable interest in investigating the particle polarization in the relativistic fluid produced in heavy-ion collisions at GeV/TeV energies. Among other sources of spin polarization phenomena, the Debye mass of a medium plays a crucial role in particle polarization. Any modification brought to the effective mass due to the temperature, strong magnetic field ($\textit{eB}$), baryonic chemical potential ( $$\mu _{B}$$ ), medium anisotropy ( $$\xi $$ ), and vorticity, etc., certainly affects the particle spin polarization. In this work, we explore the global hyperon spin polarization and the spin alignment of vector mesons corresponding to the strong magnetic field, baryonic chemical potential, and medium anisotropy. We find that the degree of spin polarization is flavor-dependent for hyperons. Meanwhile, vector meson spin alignment depends on the hadronization mechanisms of initially polarized quarks and anti-quarks. Medium anisotropy significantly changes the degree of spin polarization compared to the magnetic field and baryon chemical potential.

India

Bhagyarathi Sahoo

Captain Singh

Raghunath Sahoo

Impact of strong magnetic field, baryon chemical potential, and medium anisotropy on polarization and spin alignment of hadrons

Quarkonium production in ultra-relativistic collisions plays a crucial role in probing the existence of hot QCD matter. This study explores quarkonia states dissociation and regeneration in the hot QCD medium while considering momentum anisotropy. The net quarkonia decay width ( $$\Gamma _{D}$$  <math> <msub> <mi>Γ</mi> <mi>D</mi> </msub> </math>  ) arises from two essential processes: collisional damping and gluonic dissociation. The quarkonia regeneration includes the transition from octet to singlet states within the anisotropic medium. Our study utilizes a medium-modified potential that incorporates anisotropy via particle distribution functions. This modified potential gives rise to collisional damping for quarkonia due to the surrounding medium, as well as the transition of quarkonia from singlet to octet states due to interactions with gluons. Furthermore, we employ the detailed balance approach to investigate the regeneration of quarkonia within this medium. Our comprehensive analysis spans various temperature settings, transverse momentum values, and anisotropic strengths. Notably, we find that, in addition to medium temperatures and heavy quark transverse momentum, anisotropy significantly influences the dissociation and regeneration of various quarkonia states.

Mohammad Jamal

Impact of medium anisotropy on quarkonium dissociation and regeneration

A solution to the MiniBooNE excess invoking rare three-body decays of the charged pions and kaons to new states in the MeV mass scale was recently proposed as a dark-sector explanation. This class of solution illuminates the fact that, while the charged pions were focused in the target-mode run, their decay products were isotropically suppressed in the beam-dump-mode run in which no excess was observed. This suggests a new physics solution correlated to the mesonic sector. We investigate an extended set of phenomenological models that can explain the MiniBooNE excess as a dark sector solution, utilizing long-lived particles that might be produced in the three-body decays of the charged mesons and the two-body anomalous decays of the neutral mesons. Over a broad set of interactions with the long-lived particles, we show that these scenarios can be compatible with constraints from LSND, KARMEN, and MicroBooNE, and evaluate the sensitivity of the ongoing and future data taken by the Coherent CAPTAIN Mills experiment to a potential discovery in this parameter space.

Mexico

A. A. Aguilar-Arevalo

S. Biedron

J. Boissevain

M. Borrego

L. Bugel

M. Chavez-Estrada

J. M. Conrad

R. L. Cooper

A. Diaz

J. R. Distel

J. C. D’Olivo

E. Dunton

B. Dutta

D. Fields

J. R. Gochanour

M. Gold

E. Guardincerri

E. C. Huang

N. Kamp

D. Kim

K. Knickerbocker

W. C. Louis

J. T. M. Lyles

R. Mahapatra

S. Maludze

J. Mirabal

D. Newmark

P. deNiverville

V. Pandey

D. Poulson

H. Ray

E. Renner

T. J. Schaub

A. Schneider

M. H. Shaevitz

D. Smith

W. Sondheim

United Kingdom

A. M. Szelc

C. Taylor

A. Thompson

W. H. Thompson

M. Tripathi

R. T. Thornton

R. Van Berg

R. G. Van de Water

Testing meson portal dark sector solutions to the MiniBooNE anomaly at the Coherent CAPTAIN Mills experiment

Emission properties of compact astrophysical objects such as Neutron stars (NSs) are associated with crucial astronomical observables. In the current work, we obtain the mass, pressure profiles of the non-rotating NSs using the modified Tolman Oppenheimer Volkoff (TOV) system of equations in the presence of intense magnetic field. We obtain the profiles by using a specific distance-dependent magnetic field in the modified TOV equations. We employ three different equations of states (EoS) to solve the TOV equations by assuming the core of NSs comprises a hadronic matter. Employing the above profiles, we determine the cooling rates of spherically symmetric NSs as a function of time with and without including the magnetic field using the NSCool code. We have also determined the cooling rates as a function of radius for three different NSs. Furthermore, we determine the luminosity of neutrinos, axions, and photons emitting from the NSs in the presence and absence of a magnetic field for an axion mass 16 meV and three different EoS. Our comparative study indicates that the cooling rate and luminosities of neutrinos, axions, and photons change significantly due to the impact of the strong magnetic field. We also find that due to the magnetic field, the axion mass bound increases slightly compared to without a magnetic field.

Shubham Yadav

M. Mishra

Tapomoy Sarkar

Thermal evolution and axion emission properties of strongly magnetized neutron stars

The strongly interacting transient state of quark-gluon plasma (QGP) medium created in ultra-relativistic collisions survives for a duration of a few fm/c. The spacetime evolution of QGP crucially depends on the equation of state (EoS), vorticity, viscosity, and external magnetic field. In the present study, we obtain the lifetime of a vortical QGP fluid within the ambit of relativistic second-order viscous hydrodynamics. We observe that the coupling of vorticity and viscosity significantly increases the lifetime of vortical QGP. The inclusion of a static magnetic field, vorticity, and viscosity makes the evolution slower. However, the static magnetic field slightly decreases the QGP lifetime by accelerating the evolution process for a non-rotating medium. We also report the rate of change of vorticity in the QGP, which will be helpful in studying the behavior of the medium in detail.

Dushmanta Sahu

Jan-e Alam

Impact of vorticity and viscosity on the hydrodynamic evolution of hot QCD medium

We show results from the Coherent CAPTAIN Mills (CCM) 2019 engineering run which begin to constrain regions of parameter space for axionlike particles (ALPs) produced in electromagnetic particle showers in an 800 MeV proton beam dump, and further investigate the sensitivity of ongoing data-taking campaigns for the CCM200 upgraded detector. Based on beam-on background estimates from the engineering run, we make realistic extrapolations for background reduction based on expected shielding improvements, reduced beam width, and analysis-based techniques for background rejection. We obtain reach projections for two classes of signatures; ALPs coupled primarily to photons can be produced in the tungsten target via the Primakoff process, and then produce a gamma-ray signal in the liquid argon CCM detector either via inverse Primakoff scattering or decay to a photon pair. ALPs with significant electron couplings have several additional production mechanisms (Compton scattering, <math><msup><mi>e</mi><mo>+</mo></msup><msup><mi>e</mi><mo>−</mo></msup></math> annihilation, ALP-bremsstrahlung) and detection modes (inverse Compton scattering, external <math><msup><mi>e</mi><mo>+</mo></msup><msup><mi>e</mi><mo>−</mo></msup></math> pair conversion, and decay to <math><msup><mi>e</mi><mo>+</mo></msup><msup><mi>e</mi><mo>−</mo></msup></math>). In some regions, the constraint is marginally better than both astrophysical and terrestrial constraints. With the beginning of a three year run, CCM will be more sensitive to this parameter space by up to an order of magnitude for both ALP-photon and ALP-electron couplings. The CCM experiment will also have sensitivity to well-motivated parameter space of QCD axion models. It is only a recent realization that accelerator-based large volume liquid argon detectors designed for low-energy coherent neutrino and dark matter scattering searches are also ideal for probing ALPs in the unexplored <math><mo>∼</mo><mi>MeV</mi></math> mass scale.

D. S. M. Alves

N. Mishra

S. Verma

Prospects for detecting axionlike particles at the Coherent CAPTAIN-Mills experiment

We report the first results of a search for leptophobic dark matter (DM) from the Coherent–CAPTAIN-Mills (CCM) liquid argon (LAr) detector. An engineering run with 120 photomultiplier tubes (PMTs) and <math><mrow><mn>17.9</mn><mo>×</mo><msup><mrow><mn>10</mn></mrow><mrow><mn>20</mn></mrow></msup></mrow></math> protons on target (POT) was performed in fall 2019 to study the characteristics of the CCM detector. The operation of this 10-ton detector was strictly light based with a threshold of 50 keV and used coherent elastic scattering off argon nuclei to detect DM. Despite only 1.5 months of accumulated luminosity, contaminated LAr, and nonoptimized shielding, CCM’s first engineering run has already achieved sensitivity to previously unexplored parameter space of light dark matter models with a baryonic vector portal. With an expected background of 115 005 events, we observe <math><mrow><mn>115</mn><mtext> </mtext><mn>005</mn><mo>+</mo><mn>16.5</mn></mrow></math> events which is compatible with background expectations. For a benchmark mediator-to-DM mass ratio of <math><mrow><msub><mrow><mi>m</mi></mrow><mrow><msub><mrow><mi>V</mi></mrow><mrow><mi>B</mi></mrow></msub></mrow></msub><mo>/</mo><msub><mrow><mi>m</mi></mrow><mrow><mi>χ</mi></mrow></msub><mo>=</mo><mn>2.1</mn></mrow></math>, DM masses within the range <math><mrow><mn>9</mn><mtext> </mtext><mtext> </mtext><mi>MeV</mi><mo>≲</mo><msub><mrow><mi>m</mi></mrow><mrow><mi>χ</mi></mrow></msub><mo>≲</mo><mn>50</mn><mtext> </mtext><mtext> </mtext><mi>MeV</mi></mrow></math> are excluded at 90% C. L. in the leptophobic model after applying the Feldman-Cousins test statistic. CCM’s upgraded run with 200 PMTs, filtered LAr, improved shielding, and 10 times more POT will be able to exclude the remaining thermal relic density parameter space of this model, as well as probe new parameter space of other leptophobic DM models.

A. Chavez

A. Elliott

D. Evans

J. Greenwood

J. Gordon

E. Guarincerri

C. Kelsey

R. Lake

R. Moreno

H. Neog

J. Plata-Salas

K. Walker

First Leptophobic Dark Matter Search from the Coherent–CAPTAIN-Mills Liquid Argon Detector

This paper describes the operation of the Coherent CAPTAIN-Mills (CCM) detector located at the Los Alamos Neutron Science Center at Los Alamos National Laboratory. CCM is a 10-ton liquid argon detector located 20 meters from a high flux neutron/neutrino source and is designed to search for sterile neutrinos (<math><msub><mi>ν</mi><mi>s</mi></msub></math>’s) and light dark matter (LDM). An engineering run was performed in fall 2019 to study the characteristics of the CCM120 detector by searching for coherent scattering signals consistent with <math><msub><mi>ν</mi><mi>s</mi></msub></math>’s and LDM resulting from the production and decays of <math><msup><mi>π</mi><mo>+</mo></msup></math> and <math><msup><mi>π</mi><mn>0</mn></msup></math> in the tungsten target. New parameter space in a leptophobic dark matter (DM) model was excluded for DM masses between <math><mo>∼</mo><mn>2.0</mn></math> and 30 MeV. The lessons learned from this run have guided the development and construction of the new CCM200 detector that will begin operations in 2021 and significantly improve on these searches.

P. de Niverville

First dark matter search results from Coherent CAPTAIN-Mills

Proton–proton (pp) collision has been considered as a baseline to study the system produced in relativistic heavy-ion (AA) collisions with the basic assumption that no thermal medium is formed in pp collisions. This warrants a cautious analysis of the system produced in pp collisions at relativistic energies. In this work we investigate the charmonium suppression in pp collisions at  $$\sqrt{s} = 5.02$$  <math> <mrow> <msqrt> <mi>s</mi> </msqrt> <mo>=</mo> <mn>5.02</mn> </mrow> </math>  , 7 and 13 TeV energies. Further, charmonium suppression has been studied for various event multiplicities and transverse momenta by including the mechanisms of color screening, gluonic dissociation, collisional damping along with regeneration due to correlated  $$c{\bar{c}}$$  <math> <mrow> <mi>c</mi> <mover> <mrow> <mi>c</mi> </mrow> <mrow> <mo>¯</mo> </mrow> </mover> </mrow> </math>   pairs. Here we obtain a net suppression of charmonia at high-multiplicity events indicating the possibility of the formation of quark–gluon plasma in pp collisions.

Suman Deb

CERN

Charmonium suppression in ultra-relativistic proton–proton collisions at LHC energies: a hint for QGP in small systems