The moon is continuously bombarded by cosmic rays, primarily Galactic Cosmic Rays (GCR) and Solar Cosmic Rays, which generate complex secondary radiation in the lunar subsurface. Secondary radiation is a critical factor that must be considered in the design of radiation protection for future manned lunar missions and the construction of lunar research bases. Based on previous studies, this study employs the Geant4 to simulate the secondary radiation produced by nuclei from hydrogen to nickel in GCR, with a particular focus on the neutron number density and flux at a depth of 10 ms below the lunar surface. The results indicate that when the abundance of heavy elements from lithium to nickel in GCR is less than 1%, their contribution to the neutron number density exceeds 6%. Additionally, we analyzed the leakage fluxes of neutrons, gamma rays, protons, and electrons during the months of strongest and weakest solar modulation from 1951 to 2016. The total neutron leakage fluxes were 1.59 n/ $$\hbox {cm}^2$$ -s and 3.85 n/ $$\hbox {cm}^2$$ -s, respectively, with the leakage flux proportions of the three neutron types all below 2%. Furthermore, we simulated the total leakage of neutrons and gamma rays in the energy range of 10 to 10 MeV during the second extreme Solar Energetic Particle (SEP) event in 2003, which lasted for 33 h. The neutron leakage during this event was 4.6 times and 1.9 times higher than during the months of strongest and weakest solar modulation, respectively; while the gamma ray leakage was 14.5 times and 6.6 times higher, respectively.

China

Zhengbao Wei

Yongbo Huang

Yaping Cheng

Simulation of subsurface particle radiation and leakage flux on the moon from solar energetic particles and galactic cosmic rays

Direct searches for dark matter with large-scale noble liquid detectors have become sensitive enough to detect the coherent scattering of local neutrinos. This will become a very challenging background to dark matter discovery in planned future detectors. For dark matter with mass above 10 GeV, the dominant neutrino backgrounds on Earth are atmospheric neutrinos created by cosmic ray collisions with the atmosphere. In contrast, the Moon has almost no atmosphere and nearly all cosmic rays incident on the Moon first collide with the lunar surface, producing a very different neutrino spectrum. In this work we estimate the total flux and spectrum of neutrinos near the surface of the Moon. We then use this to show that a large-scale liquid xenon or argon detector located on the Moon could potentially have significantly greater sensitivity to dark matter compared to an equivalent detector on Earth due to effectively reduced neutrino backgrounds.

United States

Andréa Gaspert

Canada

Pietro Giampa

Navin McGinnis

David E. Morrissey

Dark matter direct detection on the Moon

This article reports the first observation of the Moon and the Sun shadows in the sky distribution of cosmic-ray induced muons measured by the KM3NeT/ORCA detector. The analysed data-taking period spans from February 2020 to November 2021, when the detector had 6 Detection Units deployed at the bottom of the Mediterranean Sea, each composed of 18 Digital Optical Modules. The shadows induced by the Moon and the Sun were detected at their nominal position with a statistical significance of 4.2 $$\sigma $$  <math> <mi>σ</mi> </math>   and 6.2 $$\sigma $$  <math> <mi>σ</mi> </math>  , and an angular resolution of  $$\sigma _{res}=0.49^\circ $$  <math> <mrow> <msub> <mi>σ</mi> <mrow> <mi>res</mi> </mrow> </msub> <mo>=</mo> <mn>0</mn> <mo>.</mo> <msup> <mn>49</mn> <mo>∘</mo> </msup> </mrow> </math>   and  $$\sigma _{res}=0.66^\circ $$  <math> <mrow> <msub> <mi>σ</mi> <mrow> <mi>res</mi> </mrow> </msub> <mo>=</mo> <mn>0</mn> <mo>.</mo> <msup> <mn>66</mn> <mo>∘</mo> </msup> </mrow> </math>  , respectively, consistent with the prediction of  $$0.53^\circ $$  <math> <mrow> <mn>0</mn> <mo>.</mo> <msup> <mn>53</mn> <mo>∘</mo> </msup> </mrow> </math>   from simulations. This early result confirms the effectiveness of the detector calibration, in time, position and orientation and the accuracy of the event direction reconstruction. This also demonstrates the performance and the competitiveness of the detector in terms of pointing accuracy and angular resolution.

Italy

S. Aiello

France

A. Albert

Spain

S. Alves Garre

Z. Aly

A. Ambrosone

F. Ameli

M. Andre

M. Anghinolfi

M. Anguita

M. Ardid

S. Ardid

J. Aublin

Greece

C. Bagatelas

L. Bailly-Salins

B. Baret

Netherlands

S. Pree

Y. Becherini

Morocco

M. Bendahman

F. Benfenati

E. Berbee

V. Bertin

S. Biagi

South Africa

M. Boettcher

M. Cabo

J. Boumaaza

M. Bouta

M. Bouwhuis

C. Bozza

Romania

H. Brânzaş

R. Bruijn

J. Brunner

R. Bruno

E. Buis

R. Buompane

J. Busto

B. Caiffi

D. Calvo

S. Campion

A. Capone

F. Carenini

V. Carretero

P. Castaldi

S. Celli

L. Cerisy

M. Chabab

N. Chau

A. Chen

R. Moursli

S. Cherubini

V. Chiarella

T. Chiarusi

M. Circella

R. Cocimano

J. Coelho

A. Coleiro

R. Coniglione

P. Coyle

A. Creusot

Australia

A. Cruz

G. Cuttone

R. Dallier

Germany

Y. Darras

A. Benedittis

B. Martino

R. Burgo

I. Palma

A. Dìaz

D. Diego-Tortosa

C. Distefano

A. Domi

C. Donzaud

D. Dornic

M. Dörr

E. Drakopoulou

D. Drouhin

T. Eberl

A. Eddyamoui

T. Eeden

M. Eff

D. Eijk

I. Bojaddaini

S. Hedri

A. Enzenhöfer

V. Espinosa

G. Ferrara

M. Filipović

F. Filippini

L. Fusco

J. Gabriel

T. Gal

J. Méndez

A. Soto

F. Garufi

C. Oliver

N. Geißelbrecht

L. Gialanella

E. Giorgio

A. Girardi

I. Goos

S. Gozzini

First observation of the cosmic ray shadow of the Moon and the Sun with KM3NeT/ORCA

The change of the shell structure in atomic nuclei, so-called “nuclear shell evolution”, occurs due to changes of major configurations through particle-hole excitations inside one nucleus, as well as due to variation of the number of constituent protons or neutrons. We have investigated how the shell evolution affects Gamow-Teller (GT) transitions that dominate the β decay in the region below $^{132}$Sn using the newly obtained experimental data on a long-lived isomer in $^{127}$Ag. The <math><msub><mrow><mi>T</mi></mrow><mrow><mn>1</mn><mo>/</mo><mn>2</mn></mrow></msub><mo>=</mo><mn>67.5</mn><mo>(</mo><mn>9</mn><mo>)</mo></math> ms isomer has been identified with a spin and parity of <math><mo>(</mo><mn>27</mn><mo>/</mo><msup><mrow><mn>2</mn></mrow><mrow><mo>+</mo></mrow></msup><mo>)</mo></math> at an excitation energy of <math><msubsup><mrow><mn>1942</mn></mrow><mrow><mo>−</mo><mn>20</mn></mrow><mrow><mo>+</mo><mn>14</mn></mrow></msubsup></math> keV, and found to decay via an internal transition of an E3 character, which competes with the dominant β-decay branches towards the high-spin states in $^{127}$Cd. The underlying mechanism of a strong GT transition from the $^{127}$Ag isomer is discussed in terms of configuration-dependent optimization of the effective single-particle energies in the framework of a shell-model approach.

Japan

H. Watanabe

C.X. Yuan

United Kingdom

G. Lorusso

S. Nishimura

Z.Y. Xu

T. Sumikama

P.A. Söderström

P. Doornenbal

F. Browne

G. Gey

South Korea

H.S. Jung

J. Taprogge

Hungary

Zs. Vajta

H.K. Wang

J. Wu

A. Yagi

H. Baba

G. Benzoni

K.Y. Chae

F.C.L. Crespi

N. Fukuda

R. Gernhäuser

N. Inabe

T. Isobe

A. Jungclaus

D. Kameda

G.D. Kim

Y.K. Kim

I. Kojouharov

F.G. Kondev

T. Kubo

N. Kurz

Y.K. Kwon

G.J. Lane

Z. Li

C.B. Moon

A. Montaner-Pizá

K. Moschner

F. Naqvi

M. Niikura

H. Nishibata

D. Nishimura

A. Odahara

Belgium

R. Orlandi

Z. Patel

Zs. Podolyák

H. Sakurai

H. Schaffner

G.S. Simpson

K. Steiger

H. Suzuki

H. Takeda

A. Wendt

K. Yoshinaga

Impact of shell evolution on Gamow-Teller Decay From a High-spin Long-lived Isomer in Ag

New and complimentary constraints are placed on the spin-independent interactions of dark matter with baryonic matter. Similar to the Earth and other planets, the Moon does not have any major internal heat source. We derive constraints by comparing the rate of energy deposit by dark matter annihilations in the Moon to 12 mW/m$^{2}$ as measured by the Apollo mission. For light dark matter of mass <math><mi>O</mi><mo>(</mo><mn>10</mn><mo>)</mo></math> GeV, we also examine the possibility of dark matter annihilations in the Moon limb. In this case, we place constraints by comparing the photon flux from such annihilations to that of the Fermi-LAT measurement of <math><msup><mrow><mn>10</mn></mrow><mrow><mo>−</mo><mn>4</mn></mrow></msup></math> MeV/cm$^{2}$s. This analysis excludes spin independent cross section <math><mo>≳</mo><msup><mrow><mn>10</mn></mrow><mrow><mo>−</mo><mn>37</mn></mrow></msup></math> <math><mi>c</mi><msup><mrow><mi>m</mi></mrow><mrow><mn>2</mn></mrow></msup></math> for dark matter mass between 30 and 50 GeV.

Raghuveer Garani

Peter Tinyakov

Constraints on dark matter from the Moon

The neutron-rich dysprosium isotopes $^{168}$Dy$_{102}$ and $^{169}$Dy$_{103}$ have been investigated using the EURICA γ-ray spectrometer, following production via in-flight fission of a high-intensity uranium beam in conjunction with isotope separation through the BigRIPS separator at RIBF in RIKEN Nishina Center. For $^{168}$Dy, a previously unreported isomer with a half-life of 0.57(7) μs has been identified at an excitation energy of 1378 keV, and its presence affirmed independently using γ-γ-γ coincidence data taken with Gammasphere via two-proton transfer from an enriched $^{170}$Er target performed at Argonne National Laboratory. This isomer is assigned <math><msup><mrow><mi>J</mi></mrow><mrow><mi>π</mi></mrow></msup><mo>=</mo><msup><mrow><mi>K</mi></mrow><mrow><mi>π</mi></mrow></msup><mo>=</mo><mo>(</mo><msup><mrow><mn>4</mn></mrow><mrow><mo>−</mo></mrow></msup><mo>)</mo></math> based on the measured transition strengths, decay patterns, and the energy systematics for two-quasiparticle states in <math><mi>N</mi><mo>=</mo><mn>102</mn></math> isotones. The underlying mechanism of two-quasiparticle excitations in the doubly midshell region is discussed in comparison with the deformed QRPA and multi-quasiparticle calculations. In $^{169}$Dy, the <math><mi>B</mi><mo>(</mo><mi>E</mi><mn>2</mn><mo>)</mo></math> value for the transition de-exciting the previously unreported <math><msup><mrow><mi>K</mi></mrow><mrow><mi>π</mi></mrow></msup><mo>=</mo><mo>(</mo><mn>1</mn><mo>/</mo><msup><mrow><mn>2</mn></mrow><mrow><mo>−</mo></mrow></msup><mo>)</mo></math> isomeric state at 166 keV to the <math><msup><mrow><mi>K</mi></mrow><mrow><mi>π</mi></mrow></msup><mo>=</mo><mo>(</mo><mn>5</mn><mo>/</mo><msup><mrow><mn>2</mn></mrow><mrow><mo>−</mo></mrow></msup><mo>)</mo></math> ground state is approximately two orders of magnitude larger than the E2 strength for the corresponding isomeric-decay transition in the <math><mi>N</mi><mo>=</mo><mn>103</mn></math> isotone $^{173}$Yb, suggesting the presence of a significant γ-vibrational admixture with a dominant neutron one-quasiparticle component in the isomeric state.

G.X. Zhang

G.D. Dracoulis

P.H. Regan

P.M. Walker

K. Yoshida

H. Kanaoka

Z. Korkulu

P.S. Lee

Hong Kong

J.J. Liu

Interplay of quasiparticle and vibrational excitations: First observation of isomeric states in Dy and Dy