arXiv subjects

F. H. Heinsius

Publications and source records attributed to F. H. Heinsius.

At least 127 records · Page 7Linked to original sources

arXiv2017

Study of $J/ψ$ and $ψ(3686)\rightarrowΣ(1385)^{0}\barΣ(1385)^{0}$ and $Ξ^0\barΞ^{0}$

We study the decays of $J/ψ$ and $ψ(3686)$ to the final states $Σ(1385)^{0}\barΣ(1385)^{0}$ and $Ξ^0\barΞ^{0}$ based on a single baryon tag method using data samples of $(1310.6 \pm 7.0) \times 10^{6}$ $J/ψ$ and $(447.9 \pm 2.9) \times 10^{6}$ $ψ(3686)$ events collected with the BESIII detector at the BEPCII collider. The decays to $Σ(1385)^{0}\barΣ(1385)^{0}$ are observed for the first time. The measured branching fractions of $J/ψ$ and $ψ(3686)\rightarrowΞ^0\barΞ^{0}$ are in good agreement with, and much more precise, than the previously published results. The angular parameters for these decays are also measured for the first time. The measured angular decay parameter for $J/ψ\rightarrowΣ(1385)^{0}\barΣ(1385)^{0}$, $α=-0.64 \pm 0.03 \pm 0.10$, is found to be negative, different to the other decay processes in this measurement. In addition, the "12\% rule" and isospin symmetry in the $J/ψ$ and $ψ(3686)\rightarrowΞ\barΞ$ and $Σ(1385)\barΣ(1385)$ systems are tested.

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arXiv2017

Evidence for $e^{+}e^{-} \to γη_c(1S)$ at center-of-mass energies between 4.01 and 4.60 GeV

We present first evidence for the process $e^+e^-\to γη_c(1S)$ at six center-of-mass energies between 4.01 and 4.60~GeV using data collected by the BESIII experiment operating at BEPCII. These data sets correspond to a total integrated luminosity of 4.6~fb$^{-1}$. We measure the Born cross section at each energy using a combination of twelve $η_c(1S)$ decay channels. Because the significance of the signal is marginal at each energy ($\le3.0σ$), we also combine all six energies under various assumptions for the energy-dependence of the cross section. If the process is assumed to proceed via the $Y(4260)$, we measure a peak Born cross section $σ_{\mathrm{ peak}}(e^+e^-\toγη_c(1S)) = 2.11 \pm 0.49 (\mathrm{stat.}) \pm 0.36 (\mathrm{syst.})$~pb with a statistical significance of 4.2$σ$.

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arXiv2017

Study of $J/ψ$ and $ψ(3686)$ decay to $Λ\barΛ$ and $Σ^0\barΣ^0$ final states

Using $1310.6\times10^6$ $J/ψ$ and $447.9\times10^6$ $ψ(3686)$ events collected with the BESIII detector at the BEPCII $e^{+}e^{-}$ collider, the branching fractions and the angular distributions of $J/ψ$ and $ψ(3686)$ decays to $Λ\barΛ$ and $Σ^0\barΣ^0$ final states are measured. The branching fractions are in agreement with, and much more precise than, the averages of previously published results. The polar angular distributions of $ψ(3686)$ decays are measured for the first time, while those of $J/ψ$ decays are measured with much improved precision. In addition, the ratios of branching fractions $\frac{\mathcal{B}(ψ(3686)\toΛ\barΛ)}{\mathcal{B}(J/ψ\toΛ\barΛ)}$ and $\frac{\mathcal{B}(ψ(3686)\toΣ^0\barΣ^0)}{\mathcal{B}(J/ψ\toΣ^0\barΣ^0)}$ are determined to test the "12\% rule".

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arXiv2017

First measurement of transverse-spin-dependent azimuthal asymmetries in the Drell-Yan process

The first measurement of transverse-spin-dependent azimuthal asymmetries in the pion-induced Drell-Yan (DY) process is reported. We use the CERN SPS 190 GeV/$c$, $π^{-}$ beam and a transversely polarized ammonia target. Three azimuthal asymmetries giving access to different transverse-momentum-dependent (TMD) parton distribution functions (PDFs) are extracted using dimuon events with invariant mass between 4.3 GeV/$c^2$ and 8.5 GeV/$c^2$. The observed sign of the Sivers asymmetry is found to be consistent with the fundamental prediction of Quantum Chromodynamics (QCD) that the Sivers TMD PDFs extracted from DY have a sign opposite to the one extracted from semi-inclusive deep-inelastic scattering (SIDIS) data. We present two other asymmetries originating from the pion Boer-Mulders TMD PDFs convoluted with either the nucleon transversity or pretzelosity TMD PDFs. These DY results are obtained at a hard scale comparable to that of a recent COMPASS SIDIS measurement and hence allow unique tests of fundamental QCD universality predictions.

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arXiv2017

Analysis of $D^+\to\bar K^0e^+ν_e$ and $D^+\toπ^0e^+ν_e$ Semileptonic Decays

Using 2.93~fb$^{-1}$ of data taken at 3.773 GeV with the BESIII detector operated at the BEPCII collider, we study the semileptonic decays $D^+ \to \bar K^0e^+ν_e$ and $D^+ \to π^0 e^+ν_e$. We measure the absolute decay branching fractions $\mathcal B(D^+ \to \bar K^0e^+ν_e)=(8.60\pm0.06\pm 0.15)\times10^{-2}$ and $\mathcal B(D^+ \to π^0e^+ν_e)=(3.63\pm0.08\pm0.05)\times10^{-3}$, where the first uncertainties are statistical and the second systematic. We also measure the differential decay rates and study the form factors of these two decays. With the values of $|V_{cs}|$ and $|V_{cd}|$ from Particle Data Group fits assuming CKM unitarity, we obtain the values of the form factors at $q^2=0$, $f^K_+(0) = 0.725\pm0.004\pm 0.012$ and $f^π_+(0) = 0.622\pm0.012\pm 0.003$. Taking input from recent lattice QCD calculations of these form factors, we determine values of the CKM matrix elements $|V_{cs}|=0.944 \pm 0.005 \pm 0.015 \pm 0.024$ and $|V_{cd}|=0.210 \pm 0.004 \pm 0.001 \pm 0.009$, where the third uncertainties are theoretical.

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arXiv2017

Observation of $Λ^+_{c}\to nK^0_Sπ^+$

We report the first direct measurement of decays of the $Λ^+_c$ baryon involving the neutron. The analysis is performed using 567 pb$^{-1}$ of $e^+e^-$ collision data collected at $\sqrt{s}=4.599$ GeV with the BESIII detector at the BEPCII collider. We observe the decay $Λ^+_{c}\rightarrow n K^0_Sπ^+$ and measure the absolute branching fraction to be $\mathcal{B}({Λ^+_{c}\rightarrow n K^0_Sπ^+})=(1.82\pm0.23({\rm stat})\pm0.11({\rm syst}))\%$. A comparison to $\mathcal{B}({Λ^+_{c}\rightarrow p(\bar{K}π)^0})$ provides an important test of isospin symmetry and final state interactions.

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arXiv2017

Evidence of Two Resonant Structures in $e^+ e^- \to π^+ π^- h_c$

The cross sections of $e^{+}e^{-}\toπ^{+}π^{-}h_c$ at center-of-mass energies from 3.896 to 4.600 GeV are measured using data samples collected with the BESIII detector operating at the Beijing Electron Positron Collider. The cross sections are found to be of the same order of magnitude as those of $e^{+}e^{-}\toπ^{+}π^{-}J/ψ$ and $e^{+}e^{-}\toπ^{+}π^{-}ψ(2S)$, but the line shape is inconsistent with the $Y$ states observed in the latter two modes. Two structures are observed in the $e^{+}e^{-}\toπ^{+}π^{-}h_c$ cross sections around 4.22 and 4.39 GeV/$c^{2}$, which we call $Y(4220)$ and $Y(4390)$, respectively. A fit with a coherent sum of two Breit-Wigner functions results in a mass of $(4218.4^{+5.5}_{-4.5}\pm0.9)$ MeV/$c^{2}$ and a width of $(66.0^{+12.3}_{-8.3}\pm0.4)$ MeV for the $Y(4220)$, and a mass of $(4391.6^{+6.3}_{-6.8}\pm1.0)$ MeV/$c^{2}$ and a width of $(139.5^{+16.2}_{-20.6}\pm0.6)$ MeV for the $Y(4390)$, where the first uncertainties are statistical and the second ones systematic. The statistical significance of $Y(4220)$ and $Y(4390)$ is 10$σ$ over one structure assumption.

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arXiv2017

Amplitude analysis of the $χ_{c1} \to ηπ^+π^-$ decays

Using $448.0 \times 10^6$~$ψ(3686)$ events collected with the BESIII detector, an amplitude analysis is performed for $ψ(3686)\toγχ_{c1}$, $χ_{c1}\toηπ^+π^-$ decays. The most dominant two-body structure observed is $a_0(980)^{\pm}π^{\mp}$; $a_0(980)^{\pm}\toηπ^{\pm}$. The $a_0(980)$ line shape is modeled using a dispersion relation, and a significant non-zero $a_0(980)$ coupling to the $η^{\prime}π$ channel is measured. We observe $χ_{c1}\to a_2(1700)π$ production for the first time, with a significance larger than 17$σ$. The production of mesons with exotic quantum numbers, $J^{PC}=1^{-+}$, is investigated, and upper limits for the branching fractions $χ_{c1}\to π_1(1400)^{\pm}π^{\mp}$, $χ_{c1}\to π_1(1600)^{\pm}π^{\mp}$, and $χ_{c1}\toπ_1(2015)^{\pm}π^{\mp}$, with subsequent $π_1(X)^{\pm} \to ηπ^{\pm}$ decay, are determined.

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arXiv2017

Resonance Production and $ππ$ S-wave in $π^- + p \rightarrow π^- π^- π^+ + p_{recoil}$ at 190 GeV/c

The COMPASS collaboration has collected the currently largest data set on diffractively produced $π^-π^-π^+$ final states using a negative pion beam of 190 GeV/c momentum impinging on a stationary proton target. This data set allows for a systematic partial-wave analysis in 100 bins of three-pion mass, $0.5 < m_{3π} < 2.5$ GeV/c$^2$ , and in 11 bins of the reduced four-momentum transfer squared, $0.1 < t < 1.0$ (GeV/c)$^2$ . This two-dimensional analysis offers sensitivity to genuine one-step resonance production, i.e. the production of a state followed by its decay, as well as to more complex dynamical effects in nonresonant $3π$ production. In this paper, we present detailed studies on selected $3π$ partial waves with $J^{PC} = 0^{-+}$, $1^{++}$, $2^{-+}$, $2^{++}$, and $4^{++}$. In these waves, we observe the well-known ground-state mesons as well as a new narrow axial-vector meson $a_1(1420)$ decaying into $f_0(980) π$. In addition, we present the results of a novel method to extract the amplitude of the $π^-π^+$ subsystem with $I^{G}J^{PC} = 0^+ 0^{++}$ in various partial waves from the $π^-π^-π^+$ data. Evidence is found for correlation of the $f_0(980)$ and $f_0(1500)$ appearing as intermediate $π^- π^+$ isobars in the decay of the known $π(1800)$ and $π_2(1880)$.

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arXiv2017

Leading-order determination of the gluon polarisation from semi-inclusive deep inelastic scattering data

Using a novel analysis technique, the gluon polarisation in the nucleon is re-evaluated using the longitudinal double-spin asymmetry measured in the cross section of semi-inclusive single-hadron muoproduction with photon virtuality $Q^2>1~({\rm GeV}/c)^2$. The data were obtained by the COMPASS experiment at CERN using a 160 GeV/$c$ polarised muon beam impinging on a polarised $^6$LiD target. By analysing the full range in hadron transverse momentum $p_{\rm T}$, the different $p_{\rm T}$-dependences of the underlying processes are separated using a neural-network approach. In the absence of pQCD calculations at next-to-leading order in the selected kinematic domain, the gluon polarisation $Δg/g$ is evaluated at leading order in pQCD at a hard scale of $μ^2= \langle Q^2 \rangle = 3 ({\rm GeV}/c)^2$. It is determined in three intervals of the nucleon momentum fraction carried by gluons, $x_{\rm g}$, covering the range $0.04 \!<\! x_{ \rm g}\! <\! 0.28$~ and does not exhibit a significant dependence on $x_{\rm g}$. The average over the three intervals, $\langle Δg/g \rangle = 0.113 \pm 0.038_{\rm (stat.)}\pm 0.036_{\rm (syst.)}$ at $\langle x_{\rm g} \rangle \approx 0.10$, suggests that the gluon polarisation is positive in the measured $x_{\rm g}$ range.

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arXiv2017

Luminosity measurements for the R scan experiment at BESIII

By analyzing the large-angle Bhabha scattering events $e^{+}e^{-}$ $\to$ ($γ$)$e^{+}e^{-}$ and diphoton events $e^{+}e^{-}$ $\to$ $γγ$ for the data sets collected at center-of-mass (c.m.) energies between 2.2324 and 4.5900 GeV (131 energy points in total) with the upgraded Beijing Spectrometer (BESIII) at the Beijing Electron-Positron Collider (BEPCII), the integrated luminosities have been measured at the different c.m. energies, individually. The results are the important inputs for R value and $J/ψ$ resonance parameter measurements.

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arXiv2017

Cross section measurements of $e^{+}e^{-}\rightarrow p \bar{p} π^{0}$ at center-of-mass energies between 4.008 and 4.600 GeV

Based on $e^+e^-$ annihilation data samples collected with the BESIII detector at the BEPCII collider at 13 center of mass energies from 4.008 to 4.600 GeV, measurements of the Born cross section of $e^{+}e^{-}\rightarrow p \bar{p} π^{0}$ are performed. No significant resonant structure is observed in the measured energy-dependent cross section. The upper limit on the Born cross section of $e^{+}e^{-}\rightarrow Y(4260) \rightarrow p \bar{p} π^{0}$ at the 90\% C.L. is determined to be 0.01 pb.

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arXiv2017

First measurement of the Sivers asymmetry for gluons from SIDIS data

The Sivers function describes the correlation between the transverse spin of a nucleon and the transverse motion of its partons. It was extracted from measurements of the azimuthal asymmetry of hadrons produced in semi-inclusive deep inelastic scattering of leptons off transversely polarised nucleon targets, and it turned out to be non-zero for quarks. In this letter the evaluation of the Sivers asymmetry for gluons in the same process is presented. The analysis method is based on a Monte Carlo simulation that includes three hard processes: photon-gluon fusion, QCD Compton scattering and leading-order virtual-photon absorption process. The Sivers asymmetries of the three processes are simultaneously extracted using the LEPTO event generator and a neural network approach. The method is applied to samples of events containing at least two hadrons with large transverse momentum from the COMPASS data taken with a 160 GeV/$c$ muon beam scattered off transversely polarised deuterons and protons. With a significance of more than two standard deviations a negative value is obtained for the gluon Sivers asymmetry. The result of a similar analysis for a Collins-like asymmetry for gluons is consistent with zero.

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arXiv2016

Observation of a new narrow axial-vector meson $a_1(1420)$

The COMPASS collaboration at CERN has measured diffractive dissociation of 190 GeV/$c$ pions into the $π^-π^-π^+$ final state using a stationary hydrogen target. A partial-wave analysis (PWA) was performed in bins of $3π$ mass and four-momentum transfer using the isobar model and the so far largest PWA model consisting of 88 waves. A narrow $J^{PC} = 1^{++}$ signal is observed in the $f_0(980)\,π$ channel. We present a resonance-model study of a subset of the spin-density matrix selecting $3π$ states with $J^{PC} = 2^{++}$ and $4^{++}$ decaying into $ρ(770)\,π$ and with $J^{PC} = 1^{++}$ decaying into $f_0(980)\,π$. We identify a new $a_1$ meson with mass $(1414^{+15}_{-13})$ MeV/$c^2$ and width $(153^{+8}_{-23})$ MeV/$c^2$. Within the final states investigated in our analysis, we observe the new $a_1(1420)$ decaying only into $f_0(980)\,π$, suggesting its exotic nature.

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arXiv2016

Measurements of the branching fractions for $D^+\to K^0_SK^0_SK^+$, $K^0_SK^0_Sπ^+$ and $D^0\to K^0_SK^0_S$, $K^0_SK^0_SK^0_S$

By analyzing $2.93\ \rm fb^{-1}$ of data taken at the $ψ(3770)$ resonance peak with the BESIII detector, we measure the branching fractions for the hadronic decays $D^+\to K^0_SK^0_S K^+$, $D^+\to K^0_SK^0_S π^+$, $D^0\to K^0_S K^0_S$ and $D^0\to K^0_SK^0_SK^0_S$. They are determined to be ${\mathcal B}(D^+\to K^0_SK^0_SK^+)=(2.54 \pm 0.05_{\rm stat.} \pm 0.12_{\rm sys.})\times 10^{-3}$, ${\mathcal B}(D^+\to K^0_SK^0_Sπ^+)=(2.70 \pm 0.05_{\rm stat.} \pm 0.12_{\rm sys.})\times 10^{-3}$, ${\mathcal B}(D^0\to K^0_SK^0_S)=(1.67 \pm 0.11_{\rm stat.} \pm 0.11_{\rm sys.})\times 10^{-4}$ and ${\mathcal B}(D^0\to K^0_SK^0_SK^0_S)=(7.21 \pm 0.33_{\rm stat.} \pm 0.44_{\rm sys.})\times 10^{-4}$, where the second one is measured for the first time and the others are measured with significantly improved precision over the previous measurements.

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arXiv2016

Final COMPASS results on the deuteron spin-dependent structure function $g_1^{\rm d}$ and the Bjorken sum rule

Final results are presented from the inclusive measurement of deep-inelastic polarised-muon scattering on longitudinally polarised deuterons using a $^6$LiD target. The data were taken at $160~{\rm GeV}$ beam energy and the results are shown for the kinematic range $1~({\rm GeV}/c)^2 < Q^2 < 100~({\rm GeV}/c)^2$ in photon virtuality, $0.004 4~{\rm GeV}/c^2$ in the mass of the hadronic final state. The deuteron double-spin asymmetry $A_1^{\rm d}$ and the deuteron longitudinal-spin structure function $g_1^{\rm d}$ are presented in bins of $x$ and $Q^2$. Towards lowest accessible values of $x$, $g_1^{\rm d}$ decreases and becomes consistent with zero within uncertainties. The presented final $g_1^{\rm d}$ values together with the recently published final $g_1^{\rm p}$ values of COMPASS are used to again evaluate the Bjorken sum rule and perform the QCD fit to the $g_1$ world data at next-to-leading order of the strong coupling constant. In both cases, changes in central values of the resulting numbers are well within statistical uncertainties. The flavour-singlet axial charge $a_0$, {which is identified in the $\overline{\rm MS}$ renormalisation scheme with the total contribution of quark helicities to the nucleon spin}, is extracted from only the COMPASS deuteron data with negligible extrapolation uncertainty: $a_0 (Q^2 = 3~({\rm GeV}/c)^2) = 0.32 \pm 0.02_{\rm stat} \pm0.04_{\rm syst} \pm 0.05_{\rm evol}$. Together with the recent results on the proton spin structure function $g_1^{\rm p}$, the results on $g_1^{\rm d}$ constitute the COMPASS legacy on the measurements of $g_1$ through inclusive spin-dependent deep inelastic scattering.

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arXiv2016

Experimental access to Transition Distribution Amplitudes with the PANDA experiment at FAIR

Baryon-to-meson Transition Distribution Amplitudes (TDAs) encoding valuable new information on hadron structure appear as building blocks in the collinear factorized description for several types of hard exclusive reactions. In this paper, we address the possibility of accessing nucleon-to-pion ($πN$) TDAs from $\bar{p}p \to e^+e^- π^0$ reaction with the future PANDA detector at the FAIR facility. At high center of mass energy and high invariant mass squared of the lepton pair $q^2$, the amplitude of the signal channel $\bar{p}p \to e^+e^- π^0$ admits a QCD factorized description in terms of $πN$ TDAs and nucleon Distribution Amplitudes (DAs) in the forward and backward kinematic regimes. Assuming the validity of this factorized description, we perform feasibility studies for measuring $\bar{p}p \to e^+e^- π^0$ with the PANDA detector. Detailed simulations on signal reconstruction efficiency as well as on rejection of the most severe background channel, i.e. $\bar{p}p \to π^+π^- π^0$ were performed for the center of mass energy squared $s = 5$ GeV$^2$ and $s = 10$ GeV$^2$, in the kinematic regions $3.0 < q^2 < 4.3$ GeV$^2$ and $5 < q^2 < 9$ GeV$^2$, respectively, with a neutral pion scattered in the forward or backward cone $| \cosθ_{π^0}| > 0.5 $ in the proton-antiproton center of mass frame. Results of the simulation show that the particle identification capabilities of the PANDA detector will allow to achieve a background rejection factor of $5\cdot 10^7$ ($1\cdot 10^7$) at low (high) $q^2$ for $s=5$ GeV$^2$, and of $1\cdot 10^8$ ($6\cdot 10^6$) at low (high) $q^2$ for $s=10$ GeV$^2$, while keeping the signal reconstruction efficiency at around $40\%$. At both energies, a clean lepton signal can be reconstructed with the expected statistics corresponding to $2$ fb$^{-1}$ of integrated luminosity. (.../...)

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arXiv2016

Measurement of the Absolute Branching Fraction for $Λ_c^+\rightarrow Λμ^+ν_μ$

We report the first measurement of the absolute branching fraction for $Λ^+_{c}\rightarrow Λμ^+ν_μ$. This measurement is based on a sample of $e^+e^-$ annihilation data at a center-of-mass energy of $\sqrt{s}=4.6$ GeV collected with the BESIII detector at the BEPCII storage rings. The sample corresponds to an integrated luminosity of 567 pb$^{-1}$. The branching fraction is determined to be $\mathcal B({Λ^+_c\rightarrow Λμ^+ν_μ})=(3.49\pm0.46({\rm stat})\pm0.27({\rm syst}))\%$. In addition, we calculate the ratio $\mathcal{B}(Λ^+_c\rightarrow Λμ^+ν_μ)/\mathcal{B}(Λ^+_c\rightarrow Λe^+ν_{e})$ to be $0.96\pm0.16({\rm stat})\pm0.04({\rm syst})$.

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