Phys. Rev. D

We report a study of the decay D0→K¯0π-e+νe based on a sample of 2.93  fb-1 e+e- annihilation data collected at the center-of-mass energy of 3.773 GeV with the BESIII detector at the BEPCII collider. The total branching fraction is determined to be B(D0→K¯0π-e+νe)=(1.434±0.029(stat.)±0.032(syst.))%, which is the most precise to date. According to a detailed analysis of the involved dynamics, we find this decay is dominated with the K*(892)- contribution and present an improved measurement of its branching fraction to be B(D0→K*(892)-e+νe)=(2.033±0.046(stat.)±0.047(syst.))%. We further access their hadronic form-factor ratios for the first time as rV=V(0)/A1(0)=1.46±0.07(stat.)±0.02(syst.) and r2=A2(0)/A1(0)=0.67±0.06(stat.)±0.01(syst.). In addition, we observe a significant K¯0π-  S-wave component accounting for (5.51±0.97(stat.)±0.62(syst.))% of the total decay rate.

Phys. Rev. Lett.

Using a 3.19  fb-1 data sample collected at an e+e- center-of-mass energy of Ecm=4.178  GeV with the BESIII detector, we measure the branching fraction of the leptonic decay Ds+→μ+νμ to be BDs+→μ+νμ=(5.49±0.16stat±0.15syst)×10-3. Combining our branching fraction with the masses of the Ds+ and μ+ and the lifetime of the Ds+, we determine fDs+|Vcs|=246.2±3.6stat±3.5syst  MeV. Using the c→s quark mixing matrix element |Vcs| determined from a global standard model fit, we evaluate the Ds+ decay constant fDs+=252.9±3.7stat±3.6syst  MeV. Alternatively, using the value of fDs+ calculated by lattice quantum chromodynamics, we find |Vcs|=0.985±0.014stat±0.014syst. These values of BDs+→μ+νμ, fDs+|Vcs|, fDs+ and |Vcs| are each the most precise results to date.

Izv.Akad.Nauk Arm.SSR Fiz.

Owing to the growing interest in the low-energy nuclear physics, it becomes relevant to enhance the potential of the experimental facilities at Yerevan Physics Institute (YerPhI). The complex unit based on the linear electron accelerator LUE-75 (ARUS synchrotron injector) for applied and fundamental experiments with electron beams, the intensity and energy of which can vary in a wide range of 10$^{–18}$–10$^{–5}$ А and 10–50 MeV, has been created. In recent years, the regimes developed at LUE-75 were applied to obtain the controllable electron beams of extremely low intensity used for calibration of detectors.

Phys. Part. Nucl. Lett.

Experimental results on pion decays obtained with the PIBETA spectrometer at the Paul Scherrer Institute (PSI) are reviewed. For pion beta decay π$^{+}$ → π$^{0}$е$^{+}$ν (πβ), a precision measurement of relative probability yields Г(πβ) = [1.036 ± 0.004(stat) ± 0.004(syst) ± 0.003(π$^{+}$→е$^{+}$ν)] × 10$^{–8}$, which implies V$_{ud}$ = 0.9728(30) for the corresponding element of the Cabibbo–Kobayashi–Maskawa mixing matrix. Using a sample of 65 × 10$^{3}$ events, relative probability of the π$^{+}$→е$^{+}$νγ radiative pion decay (RPD) in the kinematic region of E$_{γ}$ > 10 MeV and θ$_{eγ}$ > 40° is measured as B$^{exp}$ = 73.86(54) × 10$^{–8}$. A statistical analysis of measured E$_{e+}$ and E$_{γ}$ distributions for this decay yield the values F$_{V}$ = 0.0258(17) and F$_{A}$ = 0.0117(17) for the pion weak formfactors. Assuming that F$_{V}$ linearly depends on the е$^{+}$ν invariant mass q$^{2}$ as F$_{V}$(q$^{2}$) = F$_{V}$(0)(1 + aq$^{2}$), the slope parameter is extracted as а = 0.10(6). The pion polarizability and neutral-pion lifetime are estimated as α$_{E}$ = 2.78(10) × 10$^{–4}$ fm$^{3}$ and τ(π$^{0}$) = (8.5 ± 1.1) × 10$^{–17}$ s, respectively. The data for decays π$^{+}$→ е$^{+}$ ν and ${\mu ^ + } \to {e^ + }v\bar v\gamma $ have been collected and are being processed. The follow-up PEN experiment aims at reducing the uncertainty on the π$^{+}$ → е$^{+}$ ν relative probability by almost an order of magnitude (to 5 × 10$^{–4}$).

Phys. Rev. D

The cross section of the process e+e-→K+K- is measured at a number of center-of-mass energies s from 2.00 to 3.08 GeV with the BESIII detector at the Beijing Electron Positron Collider (BEPCII). The results provide the best precision achieved so far. A resonant structure around 2.2 GeV is observed in the cross section line shape. A Breit-Wigner fit yields a mass of M=2239.2±7.1±11.3  MeV/c2 and a width of Γ=139.8±12.3±20.6  MeV, where the first uncertainties are statistical and the second ones are systematic. In addition, the timelike electromagnetic form factor of the kaon is determined at the individual center-of-mass energy points.

Phys. Rev. Lett.

The adapted DIRAC experiment at the CERN PS accelerator observed for the first time long-lived hydrogenlike π+π- atoms, produced by protons hitting a beryllium target. A part of these atoms crossed the gap of 96 mm between the target and a 2.1  μm thick platinum foil, in which most of them dissociated. Analyzing the observed number of atomic pairs, nAL=436-61+157|tot, the lifetime of the 2p state is found to be τ2p=(0.45-0.30+1.08|tot)×10-11  s, not contradicting the corresponding QED 2p state lifetime τ2pQED=1.17×10-11  s. This lifetime value is three orders of magnitude larger than our previously measured value of the π+π- atom ground state lifetime τ=(3.15-0.26+0.28|tot)×10-15  s. Further studies of long-lived π+π- atoms will allow us to measure energy differences between p and s atomic states and so to discriminate between the isoscalar and isotensor ππ scattering lengths with the aim to check QCD predictions.

Phys.Lett.B

The results of a search for a standard model-like Higgs boson in the mass range between 70 and 110 GeV decaying into two photons are presented. The analysis uses the data set collected with the CMS experiment in proton-proton collisions during the 2012 and 2016 LHC running periods. The data sample corresponds to an integrated luminosity of 19.7 (35.9)fb−1 at s=8 (13) TeV. The expected and observed 95% confidence level upper limits on the product of the cross section and branching fraction into two photons are presented. The observed upper limit for the 2012 (2016) data set ranges from 129 (161) fb to 31 (26) fb. The statistical combination of the results from the analyses of the two data sets in the common mass range between 80 and 110 GeV yields an upper limit on the product of the cross section and branching fraction, normalized to that for a standard model-like Higgs boson, ranging from 0.7 to 0.2, with two notable exceptions: one in the region around the Z boson peak, where the limit rises to 1.1, which may be due to the presence of Drell–Yan dielectron production where electrons could be misidentified as isolated photons, and a second due to an observed excess with respect to the standard model prediction, which is maximal for a mass hypothesis of 95.3 GeV with a local (global) significance of 2.8 (1.3) standard deviations.

Chin. Phys. C

We study the hadronic decays of to the final states and , using an annihilation data sample of 567 pb-1 taken at a center-of-mass energy of 4.6 GeV with the BESIII detector at the BEPCII collider. We find evidence for the decays and with statistical significance of and , respectively. Normalizing to the reference decays and , we obtain the ratios of the branching fractions and to be and , respectively. The upper limits at the 90% confidence level are set to be and . Using BESIII measurements of the branching fractions of the reference decays, we determine % (<0.68%) and % (<1.9%). Here, the first uncertainties are statistical and the second systematic. The obtained branching fraction of is consistent with the previous measurement, and the branching fraction of is measured for the first time.

Mod.Phys.Lett.A

We study associated production of prompt photon and two jets at high energies in the framework of the parton Reggeization approach (PRA), which is based on multi-Regge factorization of hard processes and Lipatov’s effective theory of Reggeized gluons and quarks. In this approach, initial-state off-shell effects and transverse momenta of initial partons are included in a gauge-invariant way. We compute azimuthal angle difference spectra in γ + 2jets events and compare results with data from D0 Collaboration at the Tevatron. It was found that agreement between predictions and data can be achieved only under assumption on strong violation in transverse momentum ordering during initial-state quantum chromodynamics (QCD) evolution which corresponds multi-Regge kinematical regime instead of DGLAP picture.

Phys.Part.Nucl.Lett.

We study angular correlations in associated hadroproduction of $\Upsilon (1S)$ with the ${{D}^{ \pm }}$ and ${{D}^{0}}$ -mesons at the LHC in the Leading Order of the parton Reggeization approach. Hadronization of $b\bar {b}$ -pair to $\Upsilon (1S)$ is described within the NRQCD-factorization framework. Production of $D$ -mesons is described in the fragmentation model with scale-dependent fragmentaion functions. We have found good agreement with LHCb data for various differential distributions, except for the case of spectra on azimuthal angle differences at the small $\Delta \phi $ values. The total cross-section in our Single Parton Scattering model, calculated under conservative assumptions, accounts for almost one half of observed cross-section, thus dramatically shrinking the room for Double Parton Scattering mechanism.

PoS

The MAJORANA DEMONSTRATOR is an experiment constructed to search for neutrinoless double-beta decay in $^{76}$Ge and to demonstrate the feasibility to deploy a large-scale experiment in a phased and modular fashion. It consists of two modules of natural and $^{76}$Ge-enriched germanium detectors totalling $44.1\ \mathrm{kg}$, operating at the 4850' level of the Sanford Underground Research Facility in Lead, South Dakota, USA. Commissioning of the experiment began in June 2015, followed by data production with the full detector array in August 2016. The ultra-low background and record energy resolution achieved by the MAJORANA DEMONSTRATOR enable a sensitive neutrinoless double-beta decay search, as well as additional searches for physics beyond the Standard Model. I will discuss the design elements that enable these searches, along with the latest results, focusing on the neutrinoless double-beta decay search. I will also discuss the current status and the future plans of the MAJORANA DEMONSTRATOR, as well as the plans for a future tonne-scale $^{76}$Ge experiment.

Eur.Phys.J.A

This work measured $ \mathrm{d}\sigma/\mathrm{d}\Omega$ for neutral kaon photoproduction reactions from threshold up to a c.m. energy of 1855MeV, focussing specifically on the $ \gamma p\rightarrow K^0\Sigma^+$, $ \gamma n\rightarrow K^0\Lambda$, and $ \gamma n\rightarrow K^0 \Sigma^0$ reactions. Our results for $ \gamma n\rightarrow K^0 \Sigma^0$ are the first-ever measurements for that reaction. These data will provide insight into the properties of $ N^{\ast}$ resonances and, in particular, will lead to an improved knowledge about those states that couple only weakly to the $ \pi N$ channel. Integrated cross sections were extracted by fitting the differential cross sections for each reaction as a series of Legendre polynomials and our results are compared with prior experimental results and theoretical predictions.

Int.J.Mod.Phys.E

We have measured the differential cross-sections for the elastic as well as inelastic scattering populating the 2.43MeV (5/2−) excited state in 9Be using 3He beams at energies of 30, 40 and 47MeV on a 9Be target. The experimental results for the elastic scattering were analyzed within the framework of the optical model using the Woods–Saxon and double-folding potentials. The theoretical calculations for the concerned excited states were performed using the coupled-channel method. The optimal deformation parameters for the excited states of 9Be nucleus were extracted.

Nucl.Instrum.Meth.A

Several simple accelerator-driven system (ADS) setups were irradiated by relativistic proton and deuteron beams in last years at the Nuclotron synchrotron site of the Joint Institute for Nuclear Research (JINR) in Dubna, Russia. This paper is dedicated to a 4 GeV deuteron irradiation of a setup called Energy plus Transmutation (E+T), consisting of a lead target, natural uranium blanket, and polyethylene shielding. This paper represents the finalization of data analysis and concludes systematics of the proton and deuteron experiments carried out with the E+T setup. Activation detectors served for monitoring of proton and deuteron beams and for measurements of neutron field distribution in model ADS studies. Products of reactions with thresholds up to 106 MeV as well as non-threshold reactions were observed in the samples. The yields of the produced isotopes were determined using the gamma-ray spectrometry and compared with Monte Carlo simulations performed with the MCNPX transport code.

Phys. Rev. D

Using a low-background sample of 2.6×105  J/ψ→ωη(ω→π+π-π0,η→γγ) events, about 5 times larger statistics than previous experiments, we present a Dalitz plot analysis of the decay ω→π+π-π0. It is found that the Dalitz plot distribution differs from the pure P-wave phase space with a statistical significance of 18.9σ. The parameters from the fit to data are in reasonable agreement with those without the cross-channel effect within the dispersive framework, which indicates that the cross-channel effect in ω→π+π-π0 is not significant.

Phys. Rev. Lett.

We report on new measurements of Cabibbo-suppressed semileptonic Ds+ decays using 3.19  fb-1 of e+e- annihilation data sample collected at a center-of-mass energy of 4.178 GeV with the BESIII detector at the BEPCII collider. Our results include branching fractions B(Ds+→K0e+νe)=[3.25±0.38(stat)±0.16(syst)]×10-3 and B(Ds+→K*0e+νe)=[2.37±0.26(stat)±0.20(syst)]×10-3, which are much improved relative to previous measurements, and the first measurements of the hadronic form-factor parameters for these decays. For Ds+→K0e+νe, we obtain f+(0)=0.720±0.084(stat)±0.013(syst), and for Ds+→K*0e+νe, we find form-factor ratios rV=V(0)/A1(0)=1.67±0.34(stat)±0.16(syst) and r2=A2(0)/A1(0)=0.77±0.28(stat)±0.07(syst).

Phys. Part. Nucl.

Participation of a Joint Institute for Nuclear Research (JINR) team in the research program at the Tevatron at Fermilab is described. In their work on the upgraded CDF Run II detector, the emphasis was placed on top quark physics. The JINR team was fully engaged in the data analysis of the CDF experiment, particularly, in measuring the top quark mass in the dilepton and lepton–jet modes, in measuring the top quark charge, and in searching for the Higgs boson. The JINR team made a decisive contribution to the operation of the scintillation counter subsystem of the CDF muon trigger, to the trigger based on the vertex silicon detector for selection of events with secondary vertices and to the preshower detector of the electromagnetic calorimeter. The team was involved in the construction, upgrading, and operation of the system of scintillation counters and developed a system for the online monitoring of their parameters to ensure their effective operation in Run II. The work of the JINR researchers was highly appreciated by the international CDF collaboration.

Universe

Solar neutrinos have played a central role in the discovery of the neutrino oscillation mechanism. They still are proving to be a unique tool to help investigate the fusion reactions that power stars and further probe basic neutrino properties. The Borexino neutrino observatory has been operationally acquiring data at Laboratori Nazionali del Gran Sasso in Italy since 2007. Its main goal is the real-time study of low energy neutrinos (solar or originated elsewhere, such as geo-neutrinos). The latest analysis of experimental data, taken during the so-called Borexino Phase-II (2011-present), will be showcased in this talk—yielding new high-precision, simultaneous wide band flux measurements of the four main solar neutrino components belonging to the “pp” fusion chain (pp, pep, 7 Be, 8 B), as well as upper limits on the remaining two solar neutrino fluxes (CNO and hep).

Phys. Rev. D

The baryonic decay Ds+→pn¯ is observed, and the corresponding branching fraction is measured to be (1.21±0.10±0.05)×10-3, where the first uncertainty is statistical and second systematic. The data sample used in this analysis was collected with the BESIII detector operating at the BEPCII e+e- double-ring collider with a center-of-mass energy of 4.178 GeV and an integrated luminosity of 3.19  fb-1. The result confirms the previous measurement by the CLEO Collaboration and is of greatly improved precision. This result will improve our understanding of the dynamical enhancement of the W-annihilation topology in the charmed meson decays.

JHEP

Heavy Neutral Leptons (HNLs) are hypothetical particles predicted by many extensions of the Standard Model. These particles can, among other things, explain the origin of neutrino masses, generate the observed matter-antimatter asymmetry in the Universe and provide a dark matter candidate.

Phys.Rev.D

We report the observation of W-annihilation decay Ds+→ωπ+ and evidence for Ds+→ωK+ in a data sample corresponding to an integrated luminosity of 3.19  fb-1 collected with the BESIII detector at a center-of-mass energy s=4.178  GeV. We obtain the branching fractions B(Ds+→ωπ+)=(1.77±0.32stat±0.13sys)×10-3 with a significance of 6.7σ and B(Ds+→ωK+)=(0.87±0.24stat±0.08sys)×10-3 with a significance of 4.4σ. This measurement provides critical information to determine the nonperturbative W-annihilation amplitudes and shows the potential of searching for CP asymmetry in Ds+→ωK+.

10.1109/NSSMIC.2018.8824316

The Mu2e experiment at Fermi National Accelerator Laboratory searches for the charged-lepton flavor violation neutrino-less conversion of a negative muon into an electron in the field of an aluminum nucleus. This decay results in a mono- energetic electron with energy slightly below the muon rest mass. The design of the Mu2e experiment has been studied to reach a single event sensitivity that is four order of magnitudes better than previous experiments.The Mu2e calorimeter plays an important role to provide particle identification and an online trigger filter. After a long period of R&D conducted both at INFN and Caltech on the different components, the final technical choice has been made and the calorimeter now consists of two disks, each one made by about 700 un-doped CsI crystals read out by two large area UV-extended silicon photomultipliers.In this paper, we describe the main components of the detector and the tests performed on a large size calorimeter prototype (Module 0) that has been equipped with final crystals, photosensors, front-end electronics and cooling system.

10.18429/JACoW-RuPAC2018-THPSC24

The fast wire scanners are used for the transverse beam profile measurement in horizontal and vertical planes at the IHEP U-70 Accelerator. They cover the total range of operating beam intensities and energies of the circulating of proton and ion beams. The scheme of the scanners is based on a rotary brushless servomotor produced by the "Faulhaber" company. The speed of the fork with the carbon fiber is 16 m/s. The rotation mechanism and the control electronics was done to take into account the available radiation levels at the locations of the wire scanners. This report gives the mechatronic design of the wire scanners and provides a system overview.

10.18429/JACoW-RuPAC2018-THPSC28

Updated beam monitor system executes continuous monitoring surveillance beam losses around the IHEP U­70 accelerator. The system consists of 120 detectors. One is located upstream of each bending magnet in the median plane outside of the beam-pipe at 60 cm apart. The detectors are cheap ion chambers filled with air under barometric pressure and 1.8 liter volume. Chamber signals processing is based on digital integration and done in the framework of the U­70 Control System. Acquired data are used to facilitate tuning of the accelerator, minimize beam losses at any point of the machine circumference and consequently decrease damage for accelerator equipment. This report gives a brief description of the system and the result of run experience as an example.

10.18429/JACoW-RuPAC2018-THPSC36

Results of experimental study of the transverse beams size in the U70 synchrotron based on a fast wire scanner are given. Measurements of the transverse beam size were carried out at three special points of the U-70 synchrotron magnetic cycle: on the injection flat top (1.3 GeV proton, 0.455 GeV/u carbon); in the region of the transition energy (7.959 GeV proton); on the main flat top (49 GeV proton). Results of the fast wire scanner approbation for determination of transverse injection errors and evaluating transverse feedback efficiency are presented.