PoS

JHEP

The forward-backward charge asymmetry for the process $q\overline{q}\to Z/{\gamma}^{\ast}\to {\mu}^{+}{\mu}^{-}$ is measured as a function of the invariant mass of the dimuon system. Measurements are performed using proton proton collision data collected with the LHCb detector at $\sqrt{s}=7$ and 8 TeV, corresponding to integrated luminosities of 1 fb$^{−1}$ and 2 fb$^{−1}$ respectively. Within the Standard Model the results constrain the effective electroweak mixing angle to be ${ \sin}^2{\theta}_{\mathrm{W}}^{\mathrm{eff}}=0.23142\pm 0.00073\pm 0.00052\pm 0.00056,$ where the first uncertainty is statistical, the second systematic and the third theoretical. This result is in agreement with the current world average, and is one of the most precise determinations at hadron colliders to date.

JHEP

The first search for supersymmetry in the vector-boson fusion topology is presented. The search targets final states with at least two leptons, large missing transverse momentum, and two jets with a large separation in rapidity. The data sample corresponds to an integrated luminosity of 19.7 fb$^{−1}$ of proton-proton collisions at $\sqrt{s}=8$ TeV collected with the CMS detector at the CERN LHC. The observed dijet invariant mass spectrum is found to be consistent with the expected standard model prediction. Upper limits are set on the cross sections for chargino and neutralino production with two associated jets, assuming the supersymmetric partner of the τ lepton to be the lightest slepton and the lightest slepton to be lighter than the charginos. For a so-called compressed-mass-spectrum scenario in which the mass difference between the lightest supersymmetric particle ${\tilde{\chi}}_1^0$ and the next lightest, mass-degenerate, gaugino particles ${\tilde{\chi}}_2^0$ and ${\tilde{\chi}}_1^{\pm }$ is 50 GeV, a mass lower limit of 170 GeV is set for these latter two particles.

Phys. Rev. D

By assuming that the Λc*(2940) is a pD*0 molecular state with spin-parity JP=12+ and JP=12-, the photoproduction of charmed Λc*(2940) baryon in the γn→D-Λc*(2940)+ process is investigated with an effective Lagrangian approach. It is found that the contributions from the t-channel with D* exchange are dominant, while those from the s-channel with nucleon pole exchange give a sizeable contribution around the threshold. The contributions from the u-channel and contact term are very small. The total cross section of the γn→D-Λc*(2940)+ reaction is estimated, which indicate it is feasible to searching for the charmed Λc*(2940) baryon at the COMPASS experiment.

Phys. Rev. Lett.

We report the first measurement of the absolute branching fraction for Λc+→Λe+νe. This measurement is based on 567  pb-1 of e+e- annihilation data produced at s=4.599  GeV, which is just above the Λc+Λ¯c- threshold. The data were collected with the BESIII detector at the BEPCII storage rings. The branching fraction is determined to be B(Λc+→Λe+νe)=[3.63±0.38(stat)±0.20(syst)]%, representing a significant improvement in precision over the current indirect determination. As the branching fraction for Λc+→Λe+νe is the benchmark for those of other Λc+ semileptonic channels, our result provides a unique test of different theoretical models, which is the most stringent to date.

Nucl. Instrum. Meth. B

One of the possible ways to maintain the micrometre spatial resolution while performing ion beam analysis in the air is to increase the energy of ions. In order to explore capabilities and limitations of this approach, we have tested a range of proton beam energies (2–6MeV) using in-air STIM (Scanning Ion Transmission Microscopy) setup. Measurements of the spatial resolution dependence on proton energy have been compared with SRIM simulation and modelling of proton multiple scattering by different approaches. Results were used to select experimental conditions in which 1 micrometre spatial resolution could be obtained. High resolution in-air microbeam could be applied for IBIC (Ion Beam Induced Charge) tests of large detectors used in nuclear and high energy physics that otherwise cannot be tested in relatively small microbeam vacuum chambers.

JHEP

The production cross sections of top-quark pairs in association with massive vector bosons have been measured using data from pp collisions at $\sqrt{s}=8$ TeV. The dataset corresponds to an integrated luminosity of 20.3 fb$^{−1}$ collected by the ATLAS detector in 2012 at the LHC. Final states with two, three or four leptons are considered. A fit to the data considering the $t\overline{t}W$ and $t\overline{t}Z$ processes simultaneously yields a significance of 5.0σ (4.2σ) over the background-only hypothesis for $t\overline{t}W$ ( $t\overline{t}Z$ ) production. The measured cross sections are ${\sigma}_{t\overline{t}W}={369}_{-91}^{+100}$ fb and ${\sigma}_{t\overline{t}Z}={176}_{-52}^{+58}$ fb. The background-only hypothesis with neither $t\overline{t}W$ nor $t\overline{t}Z$ production is excluded at 7.1σ. All measurements are consistent with next-to-leading-order calculations for the $t\overline{t}W$ and $t\overline{t}Z$ processes.

Phys.Rev.Lett.

A neutral structure in the DD¯* system around the DD¯* mass threshold is observed with a statistical significance greater than 10σ in the processes e+e-→D+D*-π0+c.c. and e+e-→D0D¯*0π0+c.c. at s=4.226 and 4.257 GeV in the BESIII experiment. The structure is denoted as Zc(3885)0. Assuming the presence of a resonance, its pole mass and width are determined to be [3885.7-5.7+4.3(stat)±8.4(syst)]  MeV/c2 and [35-12+11(stat)±15(syst)]  MeV, respectively. The Born cross sections are measured to be σ[e+e-→Zc(3885)0π0,Zc(3885)0→DD¯*]=[77±13(stat)±17(syst)]  pb at 4.226 GeV and [47±9(stat)±10(syst)]  pb at 4.257 GeV. The ratio of decay rates B[Zc(3885)0→D+D*-+c.c.]/B[Zc(3885)0→D0D¯*0+c.c.] is determined to be 0.96±0.18(stat)±0.12(syst), consistent with no isospin violation in the process, Zc(3885)0→DD¯*.

Phys. Rev. Lett.

The energy spacing between the spin-doublet bound state of HeΛ4(1+,0+) was determined to be 1406±2±2  keV, by measuring γ rays for the 1+→0+ transition with a high efficiency germanium detector array in coincidence with the He4(K-,π-)HeΛ4 reaction at J-PARC. In comparison to the corresponding energy spacing in the mirror hypernucleus HΛ4, the present result clearly indicates the existence of charge symmetry breaking (CSB) in ΛN interaction. By combining the energy spacings with the known ground-state binding energies, it is also found that the CSB effect is large in the 0+ ground state but is vanishingly small in the 1+ excited state, demonstrating that the ΛN CSB interaction has spin dependence.

Phys.Rev.D

We study charged particle production (pT>0.5  GeV/c, |η|<0.8) in proton-antiproton collisions at total center-of-mass energies s=300  GeV, 900 GeV, and 1.96 TeV. We use the direction of the charged particle with the largest transverse momentum in each event to define three regions of η-ϕ space: “toward”, “away”, and “transverse.” The average number and the average scalar pT sum of charged particles in the transverse region are sensitive to the modeling of the “underlying event.” The transverse region is divided into a MAX and MIN transverse region, which helps separate the “hard component” (initial and final-state radiation) from the “beam-beam remnant” and multiple parton interaction components of the scattering. The center-of-mass energy dependence of the various components of the event is studied in detail. The data presented here can be used to constrain and improve QCD Monte Carlo models, resulting in more precise predictions at the LHC energies of 13 and 14 TeV.

Eur.Phys.J.C

The normalized differential cross section for top quark pair ( ${\mathrm{t}}\overline{{\mathrm{t}}}$ ) production is measured in pp collisions at a centre-of-mass energy of 8 $\,\text {TeV}$ at the CERN LHC using the CMS detector in data corresponding to an integrated luminosity of 19.7 $\,\text {fb}^{-1}$ . The measurements are performed in the lepton $+$ jets ( $\mathrm {e}/\mu$ $+$ jets) and in the dilepton ( $\mathrm {e}^+\mathrm {e}^-$ , $\mu ^+ \mu ^-$ , and $\mathrm {e}^\pm \mu ^{\mp }$ ) decay channels. The ${\mathrm{t}}\overline{{\mathrm{t}}}$ cross section is measured as a function of the kinematic properties of the charged leptons, the jets associated to b quarks, the top quarks, and the ${\mathrm{t}}\overline{{\mathrm{t}}}$ system. The data are compared with several predictions from perturbative quantum chromodynamic up to approximate next-to-next-to-leading-order precision. No significant deviations are observed relative to the standard model predictions.

JHEP

We present a measurement of inclusive J/ψ production in p-Pb collisions at $\sqrt{s_{\mathrm{NN}}}=5.02$ TeV as a function of the centrality of the collision, as estimated from the energy deposited in the Zero Degree Calorimeters. The measurement is performed with the ALICE detector down to zero transverse momentum, p$_{T}$, in the backward (−4.46 < y$_{cms}$ < −2.96) and forward (2.03 < y$_{cms}$ < 3.53) rapidity intervals in the dimuon decay channel and in the mid-rapidity region (−1.37 < y$_{cms}$ < 0.43) in the dielectron decay channel. The backward and forward rapidity intervals correspond to the Pb-going and p-going direction, respectively. The p$_{T}$-differential J/ψ production cross section at backward and forward rapidity is measured for several centrality classes, together with the corresponding average p$_{T}$ and p$_{T2}$ values. The nuclear modification factor is presented as a function of centrality for the three rapidity intervals, and as a function of p$_{T}$ for several centrality classes at backward and forward rapidity. At mid- and forward rapidity, the J/ψ yield is suppressed up to 40% compared to that in pp interactions scaled by the number of binary collisions. The degree of suppression increases towards central p-Pb collisions at forward rapidity, and with decreasing p$_{T}$ of the J/ψ. At backward rapidity, the nuclear modification factor is compatible with unity within the total uncertainties, with an increasing trend from peripheral to central p-Pb collisions.

Phys.Rev.C

The size of the particle emission region in high-energy collisions can be deduced using the femtoscopic correlations of particle pairs at low relative momentum. Such correlations arise due to quantum statistics and Coulomb and strong final state interactions. In this paper, results are presented from femtoscopic analyses of π±π±,K±K±,KS0KS0,pp, and p¯p¯ correlations from Pb-Pb collisions at sNN=2.76 TeV by the ALICE experiment at the LHC. One-dimensional radii of the system are extracted from correlation functions in terms of the invariant momentum difference of the pair. The comparison of the measured radii with the predictions from a hydrokinetic model is discussed. The pion and kaon source radii display a monotonic decrease with increasing average pair transverse mass mT which is consistent with hydrodynamic model predictions for central collisions. The kaon and proton source sizes can be reasonably described by approximate mT scaling.

J.Phys.Conf.Ser.

The DarkSide experiment is designed for the direct detection of Dark Matter with a double phase liquid Argon TPC operating underground at Laboratori Nazionali del Gran Sasso. The TPC is placed inside a 30 tons liquid organic scintillator sphere, acting as a neutron veto, which is in turn installed inside a 1 kt water Cherenkov detector. The current detector is running since November 2013 with a 50 kg atmospheric Argon fill and we report here the first null results of a Dark Matter search for a (1422 ± 67) kg.d exposure. This result correspond to a 90% CL upper limit on the WIMP-nucleon cross section of 6.1 × 10(-44) cm(2) (for a WIMP mass of 100 GeV/c(2)) and it's currently the most sensitive limit obtained with an Argon target.

JHEP

The production of Υ mesons in pp collisions at $\sqrt{s}=7$ and 8 TeV is studied with the LHCb detector using data samples corresponding to an integrated luminosity of 1 fb$^{−1}$ and 2 fb$^{−1}$ respectively. The production cross-sections and ratios of cross-sections are measured as functions of the meson transverse momentum p and rapidity y, for p < 30 GeV/c and 2.0 < y < 4.5.

PoS

A Multi Purpose Detector (MPD) is being constructed for the Heavy-Ion Collider at Dubna (NICA). One of the important components of MPD setup is an Electromagnetic Calorimeter, which will operate in the magnetic field of MPD solenoid and provide good energy and space resolution to detect particles in the energy range from ~100 MeV to few GeV. For this purpose the, so-called, “shashlyk” sampling structure with the fiber readout to the silicon Multi Pixel Avalanche Photodetector is used. The genuine design is similar to the one developed by us for COMPASS experiment but a number of important modifications have been introduced to better meet MPD resolution, large volume thermo-stabilization and other requirements. These details are presented in the report along with the beam test results obtained with the MPD/NICA module prototypes.

JHEP

The first measurement of CP asymmetries in the decay ${B}_s^0\to J/\psi {\overline{\mathrm{K}}}^{\ast }{(892)}^0$ and an updated measurement of its branching fraction and polarisation fractions are presented. The results are obtained using data corresponding to an integrated luminosity of 3.0 fbParseError: KaTeX parse error: Double superscript at position 5: ^{−}^̲{1} of proton-proton collisions recorded with the LHCb detector at centre-of-mass energies of 7 and 8 TeV. Together with constraints from B$^{0}$ → J/ψ ρ$^{0}$, the results are used to constrain additional contributions due to penguin diagrams in the CP -violating phase ϕ$_{s}$ , measured through B$_{s}^{0}$ decays to charmonium.

JHEP

A search for neutral Higgs bosons decaying into a $\mathrm{b}\overline{\mathrm{b}}$ quark pair and produced in association with at least one additional b quark is presented. This signature is sensitive to the Higgs sector of the minimal supersymmetric standard model (MSSM) with large values of the parameter tan β. The analysis is based on data from proton-proton collisions at a center-of-mass energy of 8 TeV collected with the CMS detector at the LHC, corresponding to an integrated luminosity of 19.7 fb$^{−1}$. The results are combined with a previous analysis based on 7 TeV data. No signal is observed. Stringent upper limits on the cross section times branching fraction are derived for Higgs bosons with masses up to 900 GeV, and the results are interpreted within different MSSM benchmark scenarios, m$_{h}^{max}$ , m$_{h}^{mod +}$ , m$_{h}^{mod −}$ , light-stau and light-stop. Observed 95% confidence level upper limits on tan β, ranging from 14 to 50, are obtained in the m$_{h}^{mod +}$ benchmark scenario.

Phys. Rev. D

In this work, inspired by the observation of charmoniumlike Zc+(4200), we study the photoproduction of charged charmoniumlike Zc+(4200) with an effective Lagrangian approach and the Regge trajectories model. The numerical results indicate that the Reggeized treatment can lead to a lower total cross section of the Zc+(4200) photoproduction and the peak position of the cross section was moved to the higher energy point when the Reggeized treatment was added. Moreover, by using the data from the COMPASS experiment and presented theoretical predictions, an upper limit of the decay width of Zc(4200)→J/ψπ is estimated. The relevant results not only shed light on the further experiment of searching for the charmoniumlike Zc(4200) state via meson photoproduction, but also provide valuable information for having a better comprehension of the nature of a charmoniumlike Zc(4200) state.

Phys. Rev. D

We present a study of the process e+e-→π±(DD¯*)∓ using data samples of 1092  pb-1 at s=4.23  GeV and 826  pb-1 at s=4.26  GeV collected with the BESIII detector at the BEPCII storage ring. With full reconstruction of the D meson pair and the bachelor π± in the final state, we confirm the existence of the charged structure Zc(3885)∓ in the (DD¯*)∓ system in the two isospin processes e+e-→π+D0D*- and e+e-→π+D-D*0. By performing a simultaneous fit, the statistical significance of Zc(3885)∓ signal is determined to be greater than 10σ, and its pole mass and width are measured to be Mpole=(3881.7±1.6(stat)±1.6(syst))  MeV/c2 and Γpole=(26.6±2.0(stat)±2.1(syst))  MeV, respectively. The Born cross section times the (DD¯*)∓ branching fraction (σ(e+e-→π±Zc(3885)∓)×Br(Zc(3885)∓→(DD¯*)∓)) is measured to be (141.6±7.9(stat)±12.3(syst))  pb at s=4.23  GeV and (108.4±6.9(stat)±8.8(syst))  pb at s=4.26  GeV. The polar angular distribution of the π±-Zc(3885)∓ system is consistent with the expectation of a quantum number assignment of JP=1+ for Zc(3885)∓.

Phys.Rev.D

Searches for both resonant and nonresonant Higgs boson pair production are performed in the hh→bbττ, γγWW* final states using 20.3  fb-1 of pp collision data at a center-of-mass energy of 8 TeV recorded with the ATLAS detector at the Large Hadron Collider. No evidence of their production is observed and 95% confidence-level upper limits on the production cross sections are set. These results are then combined with the published results of the hh→γγbb, bbbb analyses. An upper limit of 0.69 (0.47) pb on the nonresonant hh production is observed (expected), corresponding to 70 (48) times the SM gg→hh cross section. For production via narrow resonances, cross-section limits of hh production from a heavy Higgs boson decay are set as a function of the heavy Higgs boson mass. The observed (expected) limits range from 2.1 (1.1) pb at 260 GeV to 0.011 (0.018) pb at 1000 GeV. These results are interpreted in the context of two simplified scenarios of the Minimal Supersymmetric Standard Model.

Eur.Phys.J.A

Total cross sections, angular distributions, and invariant-mass distributions have been measured for the photoproduction of $\pi^{0}\pi^{0}$ pairs off free protons and off nucleons bound in the deuteron. The experiments were performed at the MAMI accelerator facility in Mainz using the Glasgow photon tagging spectrometer and the Crystal Ball/TAPS detector. The accelerator delivered electron beams of 1508 and 1557MeV, which produced bremsstrahlung in thin radiator foils. The tagged photon beam covered energies up to 1400MeV. The data from the free proton target are in good agreement with previous measurements and were only used to test the analysis procedures. The results for differential cross sections (angular distributions and invariant-mass distributions) for free and quasi-free protons are almost identical in shape, but differ in absolute magnitude up to 15%. Thus, moderate final-state interaction effects are present. The data for quasi-free neutrons are similar to the proton data in the second resonance region (final-state invariant masses up to $\approx 1550$ MeV), where both reactions are dominated by the $N(1520)3/2^{-} \rightarrow \Delta(1232)3/2^{+}\pi$ decay. At higher energies, angular and invariant-mass distributions are different. A simple analysis of the shapes of the invariant-mass distributions in the third resonance region is consistent with strong contributions of an $N^{\star}\rightarrow N\sigma$ decay for the proton, while the reaction is dominated by a sequential decay via a $\Delta\pi$ intermediate state for the neutron. The data are compared to predictions from the Two-Pion-MAID model and the Bonn-Gatchina coupled-channel analysis.

JHEP

A search for a charged Higgs boson is performed with a data sample corresponding to an integrated luminosity of 19.7 ± 0.5 fb$^{−1}$ collected with the CMS detector in proton-proton collisions at $\sqrt{s}=8$ ,TeV. The charged Higgs boson is searched for in top quark decays for m$_{H}$± < m$_{t}$ − m$_{b}$, and in the direct production pp → t(b)H$^{±}$ for m$_{H}$± > m$_{t}$ − m$_{b}$. The H$^{±}$ → τ$^{±}$ ν$_{τ}$ and H$^{±}$ → tb decay modes in the final states τ$_{h}$+jets, μτ$_{h}$, ℓ+jets, and ℓℓ’ (ℓ =e, μ) are considered in the search. No signal is observed and 95% confidence level upper limits are set on the charged Higgs boson production. A model-independent upper limit on the product branching fraction $\mathrm{\mathcal{B}}\left(\mathrm{t}\to {\mathrm{H}}^{\pm}\mathrm{b}\right)\mathrm{\mathcal{B}}\left({\mathrm{H}}^{\pm}\to {\tau}^{\pm }{\nu}_{\tau}\right)=1.2-0.15\%$ is obtained in the mass range m$_{H}$± = 80–160 GeV, while the upper limit on the cross section times branching fraction $\sigma \left(\mathrm{pp}\to \mathrm{t}\left(\mathrm{b}\right){\mathrm{H}}^{\pm}\right)\mathrm{\mathcal{B}}\left({\mathrm{H}}^{\pm}\to\ {\tau}^{\pm }{\nu}_{\tau}\right)=0.38-0.025$ pb is set in the mass range m$_{H}$+ = 180–600 GeV. Here, σ(pp → t(b)H$^{±}$) stands for the cross section sum $\sigma \left(\mathrm{pp}\to \overline{\mathrm{t}}\left(\mathrm{b}\right){\mathrm{H}}^{+}\right)+\sigma \left(\mathrm{pp}\to \mathrm{t}\left(\overline{\mathrm{b}}\right){\mathrm{H}}^{-}\right)$ . Assuming $\mathrm{\mathcal{B}}\left({\mathrm{H}}^{\pm}\to \mathrm{t}\mathrm{b}\right)=1$ , an upper limit on σ(pp → t(b)H$^{±}$) of 2.0–0.13 pb is set for m$_{H}$± = 180–600 GeV. The combination of all considered decay modes and final states is used to set exclusion limits in the m$_{H}$±−tan β parameter space in different MSSM benchmark scenarios.

Phys. Part. Nucl. Lett.

The modeling of high energy photons production in collisions of antiproton beam having E$_{beam}$ = 15 GeV with the proton target pp→ γ + {ptX} is done using the event sample simulated by PYTHIA6 generator. Such energy is high enough to consider this collision as a relativistic one and being caused by parton-parton scattering. The distribution of the set of kinematic variables and cuts which can be useful for getting the information about proton structure in the available kinematic region is obtained. The contributions of fake photons which can appear from the hadron decays as well as of the background caused by the minimum bias events and other QCD processes are estimated. The set of cuts which can be useful for separation of signal events containing the direct photons from background events is proposed.

Phys. Rev. D

This paper presents a search for Higgs bosons decaying to four leptons, either electrons or muons, via one or two light exotic gauge bosons Zd, H→ZZd→4ℓ or H→ZdZd→4ℓ. The search was performed using pp collision data corresponding to an integrated luminosity of about 20  fb−1 at the center-of-mass energy of s=8  TeV recorded with the ATLAS detector at the Large Hadron Collider. The observed data are well described by the Standard Model prediction. Upper bounds on the branching ratio of H→ZZd→4ℓ and on the kinetic mixing parameter between the Zd and the Standard Model hypercharge gauge boson are set in the range (1–9)×10-5 and (4–17)×10-2 respectively, at 95% confidence level assuming the Standard Model branching ratio of H→ZZ*→4ℓ, for Zd masses between 15 and 55 GeV. Upper bounds on the effective mass mixing parameter between the Z and the Zd are also set using the branching ratio limits in the H→ZZd→4ℓ search, and are in the range (1.5–8.7)×10-4 for 15