Observation of Electromagnetic Dalitz decays J/ψ\to P e^+e^-

Based on a sample of (225.3\pm2.8)\times 10^{6} J/\psi events collected with the BESIII detector, the electromagnetic Dalitz decays of J/\psi \to P e^+e^-(P=\eta'/\eta/\pi^0) are studied. By reconstructing the pseudoscalar mesons in various decay modes, the decays J/\psi \to \eta' e^+e^-, J/\psi \to \eta e^+e^- and J/\psi \to \pi^0 e^+e^- are observed for the first time. The branching fractions are determined to be \mathcal{B}(J/\psi\to \eta' e^+e^-) = (5.81\pm0.16\pm0.31)\times10^{-5}, \mathcal{B}(J/\psi\to \eta e^+e^-) = (1.16\pm0.07\pm0.06)\times10^{-5}, and \mathcal{B}(J/\psi\to \pi^0 e^+e^-)=(7.56\pm1.32\pm0.50)\times10^{-7}, where the first errors are statistical and the second ones systematic

No role for neutrons, muons and solar neutrinos in the DAMA annual modulation results

This paper summarizes in a simple and intuitive way why the neutrons, the muons and the solar neutrinos cannot give any significant contribution to the DAMA annual modulation results. A number of these elements have already been presented in individual papers; they are recalled here together with few simple considerations which demonstrate the incorrectness of the claim reported in Davis (PRL 113:081302, 2014 )

Investigating Earth shadowing effect with DAMA/LIBRA-phase1

In the present paper the results obtained in the investigation of possible diurnal effects for low-energy single-hit scintillation events of DAMA/LIBRA-phase1 (1.04 ton × year exposure) have been analysed in terms of an effect expected in case of dark matter (DM) candidates inducing nuclear recoils and having high cross-section with ordinary matter, which implies low DM local density in order to fulfill the DAMA/LIBRA DM annual modulation results. This effect is due to the different Earth depths crossed by those DM candidates during the sidereal day

Model independent result on possible diurnal effect in DAMA/LIBRA-phase1

The results obtained in the search for possible diurnal effect in the single-hit low energy data collected by DAMA/LIBRA-phase1 (total exposure 1.04 ton <math><mo>×</mo></math> year) deep underground at the Gran Sasso National Laboratory (LNGS) of the INFN are presented. At the present level of sensitivity the presence of any significant diurnal variation and of diurnal time structures in the data can be excluded for both the cases of solar and sidereal time. In particular, the diurnal modulation amplitude expected, because of the Earth diurnal motion, on the basis of the DAMA dark matter annual modulation results is below the present sensitivity

Search for B decays to final states with the η c meson

We report a search for B decays to selected final states with the η c meson: B ± → K ± η c π + π − , B ± → K ± η c ω , B ± → K ± η c η and B ± → K ± η c π 0 . The analysis is based on 772 × 10 6 B B ¯ $$B\overline{B}$$ pairs collected at the Υ(4 S ) resonance with the Belle detector at the KEKB asymmetric-energy e + e − collider. We set 90% confidence level upper limits on the branching fractions of the studied B decay modes, independent of intermediate resonances, in the range (0 . 6–5 . 3) × 10 −4 . We also search for molecular-state candidates in the D 0 D ¯ ∗ 0 − D ¯ 0 D ∗ 0 , D 0 D ¯ 0 + D ¯ 0 D 0 $${D}^0{\overline{D}}^{\ast 0}-{\overline{D}}^0{D}^{\ast 0},{D}^0{\overline{D}}^0+{\overline{D}}^0{D}^0$$ and D ∗ 0 D ¯ ∗ 0 + D ¯ ∗ 0 D ∗ 0 $${D}^{\ast 0}{\overline{D}}^{\ast 0}+{\overline{D}}^{\ast 0}{D}^{\ast 0}$$ combinations, neutral partners of the Z (3900) ± and Z (4020) ± , and a poorly understood state X (3915) as possible intermediate states in the decay chain, and set 90% confidence level upper limits on the product of branching fractions to the mentioned intermediate states and decay branching fractions of these states in the range (0 . 6–6 . 9) × 10 −5

Measurement of branching fractions for B J / K decays and search for a narrow resonance in the J / final state

We report an observation of the and decays using pairs collected at the resonance with the Belle detector at the KEKB asymmetric-energy collider. We obtain the branching fractions and . We search for a new narrow charmonium(-like) state in the mass spectrum and find no significant excess. We set upper limits on the product of branching fractions, , at where a -odd partner of may exist, at and assuming their known mass and width, and over a range from 3.8 to . The obtained upper limits at 90 confidence level for , , and are , , and , respectively

Bose–Einstein correlations in hadron-pairs from lepto-production on nuclei ranging from hydrogen to xenon

Bose–Einstein correlations of like-sign charged hadrons produced in deep-inelastic electron and positron scattering are studied in the HERMES experiment using nuclear targets of 1 H, 2 H, 3 He, 4 He, N, Ne, Kr, and Xe. A Gaussian approach is used to parametrize a two-particle correlation function determined from events with at least two charged hadrons of the same sign charge. This correlation function is compared to two different empirical distributions that do not include the Bose–Einstein correlations. One distribution is derived from unlike-sign hadron pairs, and the second is derived from mixing like-sign pairs from different events. The extraction procedure used simulations incorporating the experimental setup in order to correct the results for spectrometer acceptance effects, and was tested using the distribution of unlike-sign hadron pairs. Clear signals of Bose–Einstein correlations for all target nuclei without a significant variation with the nuclear target mass are found. Also, no evidence for a dependence on the invariant mass W of the photon-nucleon system is found when the results are compared to those of previous experiments

Spin density matrix elements in exclusive ω electroproduction on 1 H and 2 H targets at 27.5 GeV beam energy

Exclusive electroproduction of <math><mi mathvariant="italic">ω</mi></math> mesons on unpolarized hydrogen and deuterium targets is studied in the kinematic region of <math><mrow><msup><mi>Q</mi><mn>2</mn></msup><mo>&gt;</mo><mn>1.0</mn></mrow></math>  GeV <math><msup><mrow/><mn>2</mn></msup></math> , 3.0 GeV  <math><mrow><mo>&lt;</mo><mi>W</mi><mo>&lt;</mo></mrow></math>  6.3 GeV, and <math><mrow><mo>-</mo><msup><mi>t</mi><mo>′</mo></msup><mo>&lt;</mo><mn>0.2</mn></mrow></math>  GeV <math><msup><mrow/><mn>2</mn></msup></math> . Results on the angular distribution of the <math><mi mathvariant="italic">ω</mi></math> meson, including its decay products, are presented. The data were accumulated with the HERMES forward spectrometer during the 1996–2007 running period using the 27.6 GeV longitudinally polarized electron or positron beam of HERA. The determination of the virtual-photon longitudinal-to-transverse cross-section ratio reveals that a considerable part of the cross section arises from transversely polarized photons. Spin density matrix elements are presented in projections of <math><msup><mi>Q</mi><mn>2</mn></msup></math> or <math><mrow><mo>-</mo><msup><mi>t</mi><mo>′</mo></msup></mrow></math> . Violation of <math><mi>s</mi></math> -channel helicity conservation is observed for some of these elements. A sizable contribution from unnatural-parity-exchange amplitudes is found and the phase shift between those amplitudes that describe transverse <math><mi mathvariant="italic">ω</mi></math> production by longitudinal and transverse virtual photons, <math><mrow><msubsup><mi mathvariant="italic">γ</mi><mi>L</mi><mrow><mrow/><mo>∗</mo></mrow></msubsup><mo stretchy="false">→</mo><msub><mi mathvariant="italic">ω</mi><mi>T</mi></msub></mrow></math> and <math><mrow><msubsup><mi mathvariant="italic">γ</mi><mi>T</mi><mrow><mrow/><mo>∗</mo></mrow></msubsup><mo stretchy="false">→</mo><msub><mi mathvariant="italic">ω</mi><mi>T</mi></msub></mrow></math> , is determined for the first time. A hierarchy of helicity amplitudes is established, which mainly means that the unnatural-parity-exchange amplitude describing the <math><mrow><msubsup><mi mathvariant="italic">γ</mi><mi>T</mi><mo>∗</mo></msubsup><mo stretchy="false">→</mo><msub><mi mathvariant="italic">ω</mi><mi>T</mi></msub></mrow></math> transition dominates over the two natural-parity-exchange amplitudes describing the <math><mrow><msubsup><mi mathvariant="italic">γ</mi><mi>L</mi><mo>∗</mo></msubsup><mo stretchy="false">→</mo><msub><mi mathvariant="italic">ω</mi><mi>L</mi></msub></mrow></math> and <math><mrow><msubsup><mi mathvariant="italic">γ</mi><mi>T</mi><mo>∗</mo></msubsup><mo stretchy="false">→</mo><msub><mi mathvariant="italic">ω</mi><mi>T</mi></msub></mrow></math> transitions, with the latter two being of similar magnitude. Good agreement is found between the HERMES proton data and results of a pQCD-inspired phenomenological model that includes pion-pole contributions, which are of unnatural parity

Measurement of azimuthal hadron asymmetries in semi-inclusive deep inelastic scattering off unpolarised nucleons

Spin-averaged asymmetries in the azimuthal distributions of positive and negative hadrons produced in deep inelastic scattering were measured using the CERN SPS longitudinally polarised muon beam at 160 GeV/c and a 6 LiD target. The amplitudes of the three azimuthal modulations cos⁡ϕh , cos⁡2ϕh and sin⁡ϕh were obtained binning the data separately in each of the relevant kinematic variables x , z or pTh and binning in a three-dimensional grid of these three variables. The amplitudes of the cos⁡ϕh and cos⁡2ϕh modulations show strong kinematic dependencies both for positive and negative hadrons