Phys. Rev. D

Using data collected with the BESIII detector operating at the Beijing Electron Positron Collider, we search for the process e+e-→ηcηπ+π-. The search is performed using five large datasets recorded at center-of-mass energies of 4.23, 4.26, 4.36, 4.42, and 4.60 GeV. The ηc meson is reconstructed in 16 exclusive decay modes. No signal is observed in the ηc mass region at any center-of-mass energy. The upper limits on the reaction cross sections are determined to be 6.2, 10.8, 27.6, 22.6 and 23.7 pb at the 90% confidence level at the center-of-mass energies listed above.

Phys. Lett. B

The Λb0→Λc+K+K−π− decay is observed for the first time using a data sample of proton-proton collisions at centre-of-mass energies of s=7 and 8TeV collected by the LHCb detector, corresponding to an integrated luminosity of 3fb−1 . The ratio of branching fractions between the Λb0→Λc+K+K−π− and the Λb0→Λc+Ds− decays is measured to be B(Λb0→Λc+K+K−π−)B(Λb0→Λc+Ds−)=(9.26±0.29±0.46±0.26)×10−2, where the first uncertainty is statistical, the second systematic and the third is due to the knowledge of the Ds−→K+K−π− branching fraction. No structure on the invariant mass distribution of the Λc+K+ system is found, consistent with no open-charm pentaquark signature.

Eur. Phys. J. C

The $\Upsilon (1S)$ meson production and polarization at high energies is studied in the framework of the $k_T$-factorization approach. Our consideration is based on the non-relativistic QCD formalism for a bound states formation and off-shell production amplitudes for hard partonic subprocesses. The direct production mechanism, feed-down contributions from radiative $\chi _b(mP)$ decays and contributions from $\Upsilon (3S)$ and $\Upsilon (2S)$ decays are taken into account. The transverse momentum dependent (TMD) gluon densities in a proton were derived from the Ciafaloni–Catani–Fiorani–Marchesini evolution equation and the Kimber-Martin–Ryskin prescription. Treating the non-perturbative color octet transitions in terms of multipole radiation theory, we extract the corresponding non-perturbative matrix elements for $\Upsilon (1S)$ and $\chi _b(1P)$ mesons from a combined fit to transverse momenta distributions measured at various LHC experiments. Then we apply the extracted values to investigate the polarization parameters $\lambda _\theta $, $\lambda _\phi $ and $\lambda _{\theta \phi }$, which determine the $\Upsilon (1S)$ spin density matrix. Our predictions have a reasonably good agreement with the currently available Tevatron and LHC data within the theoretical and experimental uncertainties.

Phys. Rev. Lett.

The CUPID-Mo experiment at the Laboratoire Souterrain de Modane (France) is a demonstrator for CUPID, the next-generation ton-scale bolometric 0νββ experiment. It consists of a 4.2 kg array of 20 enriched Li2Mo100O4 scintillating bolometers to search for the lepton-number-violating process of 0νββ decay in Mo100. With more than one year of operation (Mo100 exposure of 1.17  kg×yr for physics data), no event in the region of interest and, hence, no evidence for 0νββ is observed. We report a new limit on the half-life of 0νββ decay in Mo100 of T1/2>1.5×1024  yr at 90% C.I. The limit corresponds to an effective Majorana neutrino mass ⟨mββ⟩<(0.31–0.54)  eV, dependent on the nuclear matrix element in the light Majorana neutrino exchange interpretation.

Phys.Rev.C

Exclusive dimuon production in ultraperipheral collisions (UPC), resulting from photon-photon interactions in the strong electromagnetic fields of colliding high-energy lead nuclei, $\mathrm{PbPb}(\gamma\gamma) \rightarrow \mu^+\mu^- (\mathrm{Pb}^{(\star)}\mathrm{Pb}^{(\star)} )$, is studied using $\mathcal{L}_{\mathrm{int}} = 0.48$ nb$^{-1}$ of $\sqrt{s_\mathrm{NN}}=5.02$ TeV lead-lead collision data at the LHC with the ATLAS detector. Dimuon pairs are measured in the fiducial region $p_{\mathrm{T}\mu} > 4$ GeV, $|\eta_{\mu}| < 2.4$, invariant mass $m_{\mu\mu} > 10$ GeV, and $p_{\mathrm{T,\mu\mu}} < 2$ GeV. The primary background from single-dissociative processes is extracted from the data using a template fitting technique. Differential cross sections are presented as a function of $m_{\mu\mu}$, absolute pair rapidity ($|y_{\mu\mu}|$), scattering angle in the dimuon rest frame ($|\cos \vartheta^{\star}_{\mu\mu}|$) and the colliding photon energies. The total cross section of the UPC $\gamma \gamma \rightarrow \mu^{+}\mu^{-}$ process in the fiducial volume is measured to be $\sigma_{\mathrm{fid}}^{\mu\mu} = 34.1 \! \pm \! 0.3 \mathrm{(stat.)} \! \pm \! 0.7 \mathrm{(syst.)}$ $\mu\mathrm{b}$. Generally good agreement is found with calculations from STARlight, which incorporate the leading-order Breit-Wheeler process with no final-state effects, albeit differences between the measurements and theoretical expectations are observed. In particular, the measured cross sections at larger $|y_{\mu\mu}|$ are found to be about 10-20% larger in data than in the calculations, suggesting the presence of larger fluxes of photons in the initial state. Modification of the dimuon cross sections in the presence of forward and/or backward neutron production is also studied and is found to be associated with a harder incoming photon spectrum, consistent with expectations.

JHEP

The CKM angle γ is measured for the first time from mixing-induced CP violation between $ {B}_s^0\to {D}_s^{\mp }{K}^{\pm }{\pi}^{\pm }{\pi}^{\mp } $ and $ {\overline{B}}_s^0\to {D}_s^{\pm }{K}^{\mp }{\pi}^{\mp }{\pi}^{\pm } $ decays reconstructed in proton-proton collision data corresponding to an integrated luminosity of 9 fb$^{−1}$ recorded with the LHCb detector. A time-dependent amplitude analysis is performed to extract the CP-violating weak phase γ − 2β$_{s}$ and, subsequently, γ by taking the $ {B}_s^0\hbox{-} {\overline{B}}_s^0 $ mixing phase β$_{s}$ as an external input. The measurement yields γ = (44 ± 12)° modulo 180°, where statistical and systematic uncertainties are combined. An alternative model-independent measurement, integrating over the five-dimensional phase space of the decay, yields $ \gamma =\left({44}_{-13}^{+20}\right){}^{\circ} $ modulo 180°. Moreover, the $ {B}_s^0\hbox{-} {\overline{B}}_s^0 $ oscillation frequency is measured from the flavour-specific control channel $ {B}_s^0\to {D}_s^{-}{\pi}^{+}{\pi}^{+}{\pi}^{-} $ to be ∆m$_{s}$ = (17.757 ± 0.007(stat) ± 0.008(syst)) ps$^{−1}$, consistent with and more precise than the current world-average value.[graphic not available: see fulltext]

JHEP

A search for nonresonant production of Higgs boson pairs via gluon-gluon and vector boson fusion processes in final states with two bottom quarks and two photons is presented. The search uses data from proton-proton collisions at a center-of-mass energy of $ \sqrt{s} $ = 13 TeV recorded with the CMS detector at the LHC, corresponding to an integrated luminosity of 137 fb$^{−1}$. No significant deviation from the background-only hypothesis is observed. An upper limit at 95% confidence level is set on the product of the Higgs boson pair production cross section and branching fraction into $ \gamma \gamma \mathrm{b}\overline{\mathrm{b}} $. The observed (expected) upper limit is determined to be 0.67 (0.45) fb, which corresponds to 7.7 (5.2) times the standard model prediction. This search has the highest sensitivity to Higgs boson pair production to date. Assuming all other Higgs boson couplings are equal to their values in the standard model, the observed coupling modifiers of the trilinear Higgs boson self-coupling κ$_{λ}$ and the coupling between a pair of Higgs bosons and a pair of vector bosons c$_{2V}$ are constrained within the ranges −3.3 < κ$_{λ}$< 8.5 and −1.3 < c$_{2V}$< 3.5 at 95% confidence level. Constraints on κ$_{λ}$ are also set by combining this analysis with a search for single Higgs bosons decaying to two photons, produced in association with top quark-antiquark pairs, and by performing a simultaneous fit of κ$_{λ}$ and the top quark Yukawa coupling modifier κ$_{t}$.[graphic not available: see fulltext]

Pisma Fiz.Elem.Chast.Atom.Yadra

The description of the muon capture system units with different targets (gas and solid-state) is presented. Using the muon-event selection system and high-purity germanium (HPGe) detectors, precise measurements of the time-energy distributions following ordinary muon capture in the isotopically-enriched $^{130}$Xe, $^{82}$Kr, and $^{24}$Mg nuclei were performed. The optimal parameters of the muon capture measuring system to ensure maximum muon stops in the targets under study and to collect effective statistics during measurements are reported. The system makes it possible to separate muonic X-ray events from gamma radiation with high accuracy, which is critical in such studies, and it is also suitable for future measurements with other targets.

Phys.Part.Nucl.Lett.

Lead converter was irradiated with electron beams with energies of 60, 80 and 100 MeV. And holmium samples were irradiated with a flux of bremsstrahlung, which was formed in a lead converter. The rates of about 20 photonuclear reactions in $^{165}$Ho, which are induced by bremsstrahlung, were measured. Simulations to determine the fluence of electrons, photons, neutrons for holmium samples and the reaction rates for the obtained isotopes in the samples were performed using the Geant4 code. For those radionuclides that are determined in experimental measurements, the results were compared.

Phys.Rev.D

A search is performed for the electroweak pair production of charginos and associated production of a chargino and neutralino, each of which decays through an $R$-parity-violating coupling into a lepton and a $W$, $Z$, or Higgs boson. The trilepton invariant-mass spectrum is constructed from events with three or more leptons, targeting chargino decays that include an electron or muon and a leptonically decaying $Z$ boson. The analyzed dataset corresponds to an integrated luminosity of 139 fb$^{-1}$ of proton-proton collision data produced by the Large Hadron Collider at a center-of-mass energy of $\sqrt{s}$ = 13 TeV and collected by the ATLAS experiment between 2015 and 2018. The data are found to be consistent with predictions from the Standard Model. The results are interpreted as limits at 95% confidence level on model-independent cross sections for processes beyond the Standard Model. Limits are also set on the production of charginos and neutralinos for a Minimal Supersymmetric Standard Model with an approximate $B$-$L$ symmetry. Charginos and neutralinos with masses between 100 GeV and 1100 GeV are excluded depending on the assumed decay branching fractions into a lepton (electron, muon, or $\tau$-lepton) plus a boson ($W$, $Z$, or Higgs).

Eur.Phys.J.C

This paper presents a search for dark matter in the context of a two-Higgs-doublet model together with an additional pseudoscalar mediator, a, which decays into the dark-matter particles. Processes where the pseudoscalar mediator is produced in association with a single top quark in the 2HDM+a model are explored for the first time at the LHC. Several final states which include either one or two charged leptons (electrons or muons) and a significant amount of missing transverse momentum are considered. The analysis is based on proton–proton collision data collected with the ATLAS experiment at $\sqrt{s} = 13$ TeV during LHC Run 2 (2015–2018), corresponding to an integrated luminosity of 139 $\hbox {fb}^{-1}$. No significant excess above the Standard Model predictions is found. The results are expressed as 95% confidence-level limits on the parameters of the signal models considered.

Phys.Atom.Nucl.

Neutrino astronomy offers a novel view of the non-thermal Universe and is complementary to other astronomical disciplines. The field has seen rapid progress in recent years, including the first detection of astrophysical neutrinos in the TeV–PeV energy range by IceCube and the first identified extragalactic neutrino source (TXS 0506+056). Further discoveries are aimed for with new cubic-kilometer telescopes in the Northern Hemisphere: Baikal-GVD, in Lake Baikal, and KM3NeT-ARCA, in the Mediterranean sea. The construction of Baikal-GVD proceeds as planned; the detector currently includes over 2000 optical modules arranged on 56 strings, providing an effective volume of 0.35 km${}^{3}$. We review the scientific case for Baikal-GVD, the construction plan, and first results from the partially built array.

Phys.Rev.Lett.

Using pp collision data corresponding to an integrated luminosity of 5.4  fb-1 collected with the LHCb detector at a center-of-mass energy of 13 TeV, the B0→D-D+K+π- decay is studied. A new excited Ds+ meson is observed decaying into the D+K+π- final state with large statistical significance. The pole mass and width, and the spin parity of the new state are measured with an amplitude analysis to be mR=2591±6±7  MeV, ΓR=89±16±12  MeV, and JP=0-, where the first uncertainty is statistical and the second systematic. Fit fractions for all components in the amplitude analysis are also reported. The new resonance, denoted as Ds0(2590)+, is a strong candidate to be the Ds(2S10)+ state, the radial excitation of the pseudoscalar ground-state Ds+ meson.

Eur. Phys. J. C

The paper presents a measurement of the Standard Model Higgs Boson decaying to b-quark pairs in the vector boson fusion (VBF) production mode. A sample corresponding to 126 $\hbox {fb}^{-1}$ of $\sqrt{s} = 13\,\text {TeV}$ proton–proton collision data, collected with the ATLAS experiment at the Large Hadron Collider, is analyzed utilizing an adversarial neural network for event classification. The signal strength, defined as the ratio of the measured signal yield to that predicted by the Standard Model for VBF Higgs production, is measured to be $0.95^{+0.38}_{-0.36}$ , corresponding to an observed (expected) significance of 2.6 (2.8) standard deviations from the background only hypothesis. The results are additionally combined with an analysis of Higgs bosons decaying to b-quarks, produced via VBF in association with a photon.

Phys.Rev.Lett.

A search for charged leptons with large impact parameters using $139{\mathrm{fb}}^{-1}$ of $\sqrt{s}=13\mathrm{TeV}$ $pp$ collision data from the ATLAS detector at the LHC is presented, addressing a long-standing gap in coverage of possible new physics signatures. Results are consistent with the background prediction. This search provides unique sensitivity to long-lived scalar supersymmetric lepton partners (sleptons). For lifetimes of 0.1 ns, selectron, smuon, and stau masses up to 720, 680, and $340\mathrm{GeV}$, respectively, are excluded at 95% confidence level, drastically improving on the previous best limits from LEP.

Phys. Rev. D

We report an amplitude analysis and branching fraction measurement of $D_s^{+}\to K^{+}{K}^{-}{\pi }^{+}$ decay using a data sample of $3.19{\mathrm{fb}}^{-1}$ recorded with BESIII detector at a center-of-mass energy of 4.178 GeV. We perform a model-independent partial wave analysis in the low $K^{+}{K}^{-}$ mass region to determine the $K^{+}{K}^{-}$ S-wave line shape, followed by an amplitude analysis of our very pure high-statistics sample. With the detection efficiency based on the amplitude analysis results, the absolute branching fraction is measured to be $\mathcal{B}(D_s^{+}\to K^{+}{K}^{-}{\pi }^{+})=(5.47\pm 0.08_{\mathrm{stat}}\pm 0.13_{\mathrm{sys}})\%$.

Phys. Rev. D

The rare decay η′→π+π-e+e- is studied using a sample of 1.3×109  J/ψ events collected with the BESIII detector at BEPCII in 2009 and 2012. The branching fraction is measured with improved precision to be (2.42±0.05stat±0.08syst)×10-3. Due to the inclusion of new data, this result supersedes the last BESIII result on this branching fraction. In addition, the CP-violating asymmetry in the angle between the decay planes of the π+π--pair and the e+e--pair is investigated. A measurable value would indicate physics beyond the standard model; the result is ACP=(2.9±3.7stat±1.1syst)%, which is consistent with the standard model expectation of no CP-violation. The precision is comparable to the asymmetry measurement in the KL0→π+π-e+e- decay where the observed (14±2)% effect is driven by a standard model mechanism.

Phys. Rev. Lett.

We report a study of the processes of e+e-→K+Ds-D*0 and K+Ds*-D0 based on e+e- annihilation samples collected with the BESIII detector operating at BEPCII at five center-of-mass energies ranging from 4.628 to 4.698 GeV with a total integrated luminosity of 3.7  fb-1. An excess of events over the known contributions of the conventional charmed mesons is observed near the Ds-D*0 and Ds*-D0 mass thresholds in the K+ recoil-mass spectrum for events collected at s=4.681  GeV. The structure matches a mass-dependent-width Breit-Wigner line shape, whose pole mass and width are determined as (3982.5-2.6+1.8±2.1)  MeV/c2 and (12.8-4.4+5.3±3.0)  MeV, respectively. The first uncertainties are statistical and the second are systematic. The significance of the resonance hypothesis is estimated to be 5.3  σ over the contributions only from the conventional charmed mesons. This is the first candidate for a charged hidden-charm tetraquark with strangeness, decaying into Ds-D*0 and Ds*-D0. However, the properties of the excess need further exploration with more statistics.

JCAP

Future liquid-argon DarkSide-20k and Argo detectors, designed for direct dark matter search, will be sensitive also to core-collapse supernova neutrinos, via coherent elastic neutrino-nucleus scattering. This interaction channel is flavor-insensitive with a high-cross section, enabling for a high-statistics neutrino detection with target masses of ∼50 t and ∼360 t for DarkSide-20k and Argo respectively. Thanks to the low-energy threshold of ∼0.5 keVnr achievable by exploiting the ionization channel, DarkSide-20k and Argo have the potential to discover supernova bursts throughout our galaxy and up to the Small Magellanic Cloud, respectively, assuming a 11-M☉ progenitor star. We report also on the sensitivity to the neutronization burst, whose electron neutrino flux is suppressed by oscillations when detected via charged current and elastic scattering. Finally, the accuracies in the reconstruction of the average and total neutrino energy in the different phases of the supernova burst, as well as its time profile, are also discussed, taking into account the expected background and the detector response.

PoS

PEN is an industrial polyester plastic which has become interesting for the physics community as a new type of plastic scintillator. PEN scintillates in the blue regime, which is ideal for most photosensor devices. In addition, PEN has excellent mechanical properties and very good radiopurity has been achieved. Thus, it is an ideal candidate for active structural components in low-background experiments. One possible application are holders for germanium detectors operating in cryogenic liquids (LAr, LN2). Such structures can help to reject surface and external backgrounds, boosting the sensitivity of experiments. In this contribution, the R\&D on PEN is outlined and an evaluation of the first production of PEN structures for the LEGEND-200 experiment is reported.

Phys. Rev. C

Double-beta decays of ${}^{100}\mathrm{Mo}$ from the 6.0195-year exposure of a 6.914 kg high-purity sample were recorded by the NEMO-3 experiment that searched for neutrinoless double-beta decays. These ultrarare transitions to ${}^{100}\mathrm{Ru}$ have a half-life of approximately $7\times {10}^{18}$ years and have been used to conduct the first-ever search for periodic variations of this decay mode. The Lomb-Scargle periodogram technique, and its error-weighted extension, were employed to look for periodic modulations of the half-life. Data show no evidence at the 95% confidence level of modulations with amplitude greater than 2.5% in the frequency range of $0.33225{\mathrm{yr}}^{-1}$ to $360{\mathrm{yr}}^{-1}$.

Chin.Phys.C

A search for the rare decay is performed using collision data collected with the LHCb dete-ctor at centre-of-mass energies of 7, 8 and 13 TeV, corresponding to an integrated luminosity of 9 fb−1. No significant signal of the decay is observed and an upper limit of at 90% confidence level is set on the branching fraction.

JHEP

We present the calibration strategy for the 20 kton liquid scintillator central detector of the Jiangmen Underground Neutrino Observatory (JUNO). By utilizing a comprehensive multiple-source and multiple-positional calibration program, in combination with a novel dual calorimetry technique exploiting two independent photosensors and readout systems, we demonstrate that the JUNO central detector can achieve a better than 1% energy linearity and a 3% effective energy resolution, required by the neutrino mass ordering determination.[graphic not available: see fulltext]

Eur. Phys. J. C

A search for a heavy neutral Higgs boson, A, decaying into a Z boson and another heavy Higgs boson, H, is performed using a data sample corresponding to an integrated luminosity of 139 fb$^{-1}$ from proton–proton collisions at $\sqrt{s} = 13$ $\text {TeV}$ recorded by the ATLAS detector at the LHC. The search considers the Z boson decaying into electrons or muons and the H boson into a pair of b-quarks or W bosons. The mass range considered is 230–800 $\text {GeV}$ for the A boson and 130–700 $\text {GeV}$ for the H boson. The data are in good agreement with the background predicted by the Standard Model, and therefore 95% confidence-level upper limits for $\sigma \times B(A\rightarrow ZH)\times B(H\rightarrow bb \; \text {or} \; H \rightarrow WW)$ are set. The upper limits are in the range 0.0062–0.380 pb for the $H\rightarrow bb$ channel and in the range 0.023–8.9 pb for the $H\rightarrow WW$ channel. An interpretation of the results in the context of two-Higgs-doublet models is also given.

IEEE Trans.Nucl.Sci.

In this article, development results from a new p-type high-purity germanium (HPGe) detector with a segmented n ⁺ -region are presented. The intended detector is used in spectrometry; however, its sixfold segmentation allows for the determination of the direction of individual photons emitted in the nuclear reactions from a source placed inside the detector. The capacitance and current voltage characteristics of the detector are presented. At full depletion of -1500 V, the segments' capacitance was measured to be 17 pF and leakage currents ranged between 7 and 10 pA. The energy resolution of the segments was measured with a variety of gamma sources and determined to be less than 1000 eV at 122 keV and less than 1900 eV at 1332 keV. The incident photon angle response from a radiation source placed inside the detector was also studied.