arXiv subjects

M. Albrecht

Publications and source records attributed to M. Albrecht.

At least 361 records · Page 20Linked to original sources

arXiv2017

Search for the Radiative Leptonic Decay $D^{+}\to γe^{+} ν_{e}$

Using an electron-positron collision data sample of 2.93 fb$^{-1}$ collected at a center-of-mass energy of $\sqrt{s}=3.773$ GeV with the BESIII detector, we present the first search for the radiative leptonic decay $D^{+} \rightarrow γe^{+}ν_{e}$. The analysis is performed with a double tag method. We do not observe a significant $D^{+} \rightarrow γe^{+}ν_{e}$ signal, and obtain an upper limit on the branching fraction of $D^{+} \rightarrow γe^{+}ν_{e}$ decay with the energy of radiative photon larger than 10 MeV of $3.0\times10^{-5}$ at the 90% confidence level.

hep-ex↗

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.

hep-ex↗

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.

hep-ex↗

arXiv2017

Precise measurement of the $e^+e^-\to π^+π^-J/ψ$ cross section at center-of-mass energies from 3.77 to 4.60 GeV

The cross section for the process $e^+e^-\to π^+π^-J/ψ$ is measured precisely at center-of-mass energies from 3.77 to 4.60~GeV using 9~fb$^{-1}$ of data collected with the BESIII detector operating at the BEPCII storage ring. Two resonant structures are observed in a fit to the cross section. The first resonance has a mass of $(4222.0\pm 3.1\pm 1.4)$~MeV/$c^2$ and a width of $(44.1\pm 4.3\pm 2.0)$~MeV, while the second one has a mass of $(4320.0\pm 10.4 \pm 7.0)$~MeV/$c^2$ and a width of $(101.4^{+25.3}_{-19.7}\pm 10.2)$~MeV, where the first errors are statistical and second ones are systematic. The first resonance agrees with the $Y(4260)$ resonance reported by previous experiments. The precision of its resonant parameters is improved significantly. The second resonance is observed in $e^+e^-\to π^+π^-J/ψ$ for the first time. The statistical significance of this resonance is estimated to be larger than $7.6σ$. The mass and width of the second resonance agree with the $Y(4360)$ resonance reported by the $BABAR$ and Belle experiments within errors. Finally, the $Y(4008)$ resonance previously observed by the Belle experiment is not confirmed in the description of the BESIII data.

hep-ex↗

arXiv2017

In/GaN(0001)-$\boldsymbol{{\mathsf{\left(\!\sqrt{3}\times\!\sqrt{3}\right)\!R30^{\circ}}}}$ adsorbate structure as a template for embedded (In,Ga)N/GaN monolayers and short-period superlattices

We explore an alternative way to fabricate (In,Ga)N/GaN short-period superlattices on GaN(0001) by plasma-assisted molecular beam epitaxy. We exploit the existence of an In adsorbate structure manifesting itself by a $(\sqrt{3}\times\!\sqrt{3})\text{R}30^{\circ}$ surface reconstruction observed in-situ by reflection high-energy electron diffraction. This In adlayer accommodates a maximum of 1/3 monolayer of In on the GaN surface and, under suitable conditions, can be embedded into GaN to form an In$_{0.33}$Ga$_{0.67}$N quantum sheet whose width is naturally limited to a single monolayer. Periodically inserting these quantum sheets, we synthesize (In,Ga)N/GaN short-period superlattices with abrupt interfaces and high periodicity as demonstrated by x-ray diffractometry and scanning transmission electron microscopy. The embedded quantum sheets are found to consist of single monolayers with an In content of 0.25-0.29. For a barrier thickness of 6 monolayers, the superlattice gives rise to a photoluminescence band at 3.16 eV, close to the theoretically predicted values for these structures.

cond-mat.mtrl-sci↗

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.

hep-ex↗

arXiv2017

Amplitude Analysis of the Decays $η^\prime \rightarrow π^+π^-π^0$ and $η^\prime \rightarrow π^0π^0π^0$

Based on a sample of $1.31 \times 10^9$ $J/ψ$ events collected with the BESIII detector, an amplitude analysis of the isospin-violating decays $η^\prime \rightarrow π^+π^-π^0$ and $η^\prime \rightarrow π^0π^0π^0$ is performed. A significant $P$-wave contribution from $η^\prime \rightarrow ρ^{\pm} π^{\mp}$ is observed for the first time in $η^\prime \rightarrow π^+π^-π^0$. The branching fraction is determined to be ${\mathcal B}(η^\prime \rightarrow ρ^{\pm}π^{\mp})=(7.44\pm0.60\pm1.26\pm1.84)\times 10^{-4}$, where the first uncertainty is statistical, the second systematic, and the third model dependent. In addition to the nonresonant $S$-wave component, there is a significant $σ$ meson component. The branching fractions of the combined $S$-wave components are determined to be ${\mathcal B}(η^\prime \rightarrow π^+π^-π^0)_S=(37.63\pm0.77\pm2.22\pm4.48)\times 10^{-4}$ and ${\mathcal B}(η^\prime \rightarrow π^0π^0π^0)=(35.22\pm0.82\pm2.54)\times 10^{-4}$, respectively. The latter one is consistent with previous BESIII measurements.

hep-ex↗

arXiv2016

Measurements of the absolute branching fractions for $D_{s}^{+}\rightarrowηe^{+}ν_{e}$ and $D_{s}^{+}\rightarrowη^{\prime} e^{+}ν_{e}$

By analyzing 482 pb$^{-1}$ of $e^+e^-$ collision data collected at $\sqrt s=4.009$ GeV with the BESIII detector at the BEPCII collider, we measure the absolute branching fractions for the semileptonic decays $D_{s}^{+}\toηe^{+}ν_{e}$ and $D_{s}^{+}\to η'e^{+}ν_{e}$ to be ${B}(D_{s}^{+}\rightarrowηe^{+}ν_{e})=(2.30\pm0.31\pm0.08)$\% and ${B}(D_{s}^{+}\rightarrowη'e^{+} ν_{e}) = (0.93\pm0.30\pm0.05)$\%, respectively, and their ratio $\frac{{B}(D_{s}^{+}\rightarrowη'e^{+}ν_{e})} {{B}(D_{s}^{+}\rightarrowηe^{+}ν_{e})}=0.40\pm0.14\pm0.02$, where the first uncertainties are statistical and the second ones are systematic. The results are in good agreement with previous measurements within uncertainties; they can be used to determine the $η-η'$ mixing angle and improve upon the $D_s^+$ semileptonic branching ratio precision.

hep-ex↗

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.

hep-ex↗

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. (.../...)

hep-ex↗

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 $0.96\pm0.16({\rm stat})\pm0.04({\rm syst})$.

hep-ex↗

arXiv2016

Measurement of the $D_s^+ \to \ell^+ν_\ell$ branching fractions and the decay constant $f_{D_s^+}$

Using 482~pb$^{-1}$ of $e^+e^-$ collision data collected at a center-of-mass energy of $\sqrt{s} = 4.009$ GeV with the BESIII detector, we measure the branching fractions of the decays $D_s^+\toμ^+ν_μ$ and $D_s^+\toτ^+ν_τ$. By constraining the ratio of decay rates of $D_s^+$ to $τ^+ν_τ$ and to $μ^+ν_μ$ to the Standard Model prediction, the branching fractions are determined to be $\mathcal{B}(D_s^+ \to μ^+ν_μ) = (0.495 \pm 0.067 \pm 0.026)\%$ and $\mathcal{B}(D_s^+ \to τ^+ν_τ) = (4.83 \pm 0.65 \pm 0.26)\%$. Using these branching fractions, we obtain a value for the decay constant $f_{D_s^+}$ of $(241.0 \pm 16.3 \pm 6.5)~\text{MeV}$, where the first error is statistical and the second systematic.

hep-ex↗

arXiv2016

Feasibility study for the measurement of $πN$ TDAs at PANDA in $\bar{p}p\to J/ψπ^0$

The exclusive charmonium production process in $\bar{p}p$ annihilation with an associated $π^0$ meson $\bar{p}p\to J/ψπ^0$ is studied in the framework of QCD collinear factorization. The feasibility of measuring this reaction through the $J/ψ\to e^+e^-$ decay channel with the PANDA (AntiProton ANnihilation at DArmstadt) experiment is investigated. Simulations on signal reconstruction efficiency as well as the background rejection from various sources including the $\bar{p}p\toπ^+π^-π^0$ and $\bar{p}p\to J/ψπ^0π^0$ reactions are performed with PandaRoot, the simulation and analysis software framework of the PANDA experiment. It is shown that the measurement can be done at PANDA with significant constraining power under the assumption of an integrated luminosity attainable in four to five months of data taking at the maximum design luminosity.

nucl-ex↗

arXiv2016

Feasibility studies of time-like proton electromagnetic form factors at PANDA at FAIR

Simulation results for future measurements of electromagnetic proton form factors at \PANDA (FAIR) within the PandaRoot software framework are reported. The statistical precision with which the proton form factors can be determined is estimated. The signal channel $\bar p p \to e^+ e^-$ is studied on the basis of two different but consistent procedures. The suppression of the main background channel, $\textit{i.e.}$ $\bar p p \to π^+ π^-$, is studied. Furthermore, the background versus signal efficiency, statistical and systematical uncertainties on the extracted proton form factors are evaluated using two different procedures. The results are consistent with those of a previous simulation study using an older, simplified framework. However, a slightly better precision is achieved in the PandaRoot study in a large range of momentum transfer, assuming the nominal beam conditions and detector performance.

hep-ex↗

arXiv2016

Observation of $J/ψ\to γηπ^{0}$

We present the first study of the process $J/ψ\rightarrow γηπ^{0}$ using $(223.7\pm1.4)\times10^{6}$ $J/ψ$ events accumulated with the BESIII detector at the BEPCII facility. The branching fraction for $J/ψ\rightarrow γηπ^{0}$ is measured to be $\mathcal{B}(J/ψ\rightarrow γηπ^{0}) =(2.14\pm0.18(stat)\pm0.25(syst))\times10^{-5}$. With a Bayesian approach, the upper limits of the branching fractions $\mathcal{B}(J/ψ\rightarrow γa_{0}(980),a_0(980)\rightarrowηπ^0)$ and $\mathcal{B}(J/ψ\rightarrow γa_{2}(1320),a_2(1320)\rightarrowηπ^0)$ are determined to be $2.5\times10^{-6}$ and $6.6\times10^{-6}$ at the 95\% confidence level, respectively. All of these measurements are given for the first time.

hep-ex↗

arXiv2016

Measurement of the leptonic decay width of $J/ψ$ using initial state radiation

Using a data set of 2.93 fb$^{-1}$ taken at a center-of-mass energy of $\sqrt{s}$ = 3.773 GeV with the BESIII detector at the BEPCII collider, we measure the process $e^+e^-\rightarrow J/ψγ\rightarrow μ^+μ^-γ$ and determine the product of the branching fraction and the electronic width $\mathcal B_{μμ}\cdot Γ_{ee} = (333.4 \pm 2.5_{\rm stat} \pm 4.4_{\rm sys})$~eV. Using the earlier-published BESIII result for $\mathcal B_{μμ}$ = (5.973 $\pm$ 0.007$_{\rm stat}$ $\pm$ 0.037$_{\rm sys}$)\%, we derive the $J/ψ$ electronic width $Γ_{ee}$~= (5.58 $\pm$ 0.05$_{\rm stat}$ $\pm$ 0.08$_{\rm sys}$) keV.

hep-ex↗

arXiv2016

Study of $D^{+} \to K^{-} π^+ e^+ ν_e$

We present an analysis of the decay $D^{+} \to K^{-} π^+ e^+ ν_e$ based on data collected by the BESIII experiment at the $ψ(3770)$ resonance. Using a nearly background-free sample of 18262 events, we measure the branching fraction $\mathcal{B}(D^{+} \to K^{-} π^+ e^+ ν_e) = (3.71 \pm 0.03 \pm 0.08)\%$. For $0.8<m_{Kπ}<1.0$ GeV/$c^{2}$ the partial branching fraction is $\mathcal{B}(D^{+} \to K^{-} π^+ e^+ ν_e)_{[0.8,1]} = (3.33 \pm 0.03 \pm 0.07)\%$. A partial wave analysis shows that the dominant $\bar K^{*}(892)^{0}$ component is accompanied by an \emph{S}-wave contribution accounting for $(6.05\pm0.22\pm0.18)\%$ of the total rate and that other components are negligible. The parameters of the $\bar K^{*}(892)^{0}$ resonance and of the form factors based on the spectroscopic pole dominance predictions are also measured. We also present a measurement of the $\bar K^{*}(892)^{0}$ helicity basis form factors in a model-independent way.

hep-ex↗

arXiv2016

Determination of the number of $J/ψ$ events with inclusive $J/ψ$ decays

A measurement of the number of $J/ψ$ events collected with the BESIII detector in 2009 and 2012 is performed using inclusive decays of the $J/ψ$ . The number of $J/ψ$ events taken in 2009 is recalculated to be $(223.7\pm1.4)\times 10^6$, which is in good agreement with the previous measurement, but with significantly improved precision due to improvements in the BESIII software. The number of $J/ψ$ events taken in 2012 is determined to be $(1086.9\pm 6.0)\times 10^6$. In total, the number of $J/ψ$ events collected with the BESIII detector is measured to be $(1310.6\pm 7.0)\times 10^6$, where the uncertainty is dominated by systematic effects and the statistical uncertainty is negligible.

hep-ex↗