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M. Albrecht

Publications and source records attributed to M. Albrecht.

At least 37 records · Page 2Linked to original sources
arXiv2023

Search for $\barΛ$-$Λ$ oscillations in the decay $J/ψ\to p K^- \barΛ+c.c.$

We report the first search for $\barΛ$--$Λ$ oscillations in the decay $J/ψ\to p K^- \barΛ + c.c.$ by analyzing $1.31\times10^9$ $J/ψ$ events accumulated with the BESIII detector at the BEPCII collider. The $J/ψ$ events are produced using $e^+e^-$ collisions at a center of mass energy $\sqrt{s}= 3.097$~GeV. No evidence for hyperon oscillations is observed. The upper limit for the oscillation rate of $\barΛ$ to $Λ$ hyperons is determined to be $\mathcal{P}(Λ)=\frac{\mathcal{B}(J/ψ\to pK^-Λ+c.c.)}{\mathcal{B}(J/ψ\to pK^-\barΛ+c.c.)}<4.4\times10^{-6}$ corresponding to an oscillation parameter $δm_{Λ\barΛ}$ of less than $3.8\times10^{-18}$~GeV at the 90\% confidence level.

hep-ex↗
arXiv2023

Strong Interaction Physics at the Luminosity Frontier with 22 GeV Electrons at Jefferson Lab

This document presents the initial scientific case for upgrading the Continuous Electron Beam Accelerator Facility (CEBAF) at Jefferson Lab (JLab) to 22 GeV. It is the result of a community effort, incorporating insights from a series of workshops conducted between March 2022 and April 2023. With a track record of over 25 years in delivering the world's most intense and precise multi-GeV electron beams, CEBAF's potential for a higher energy upgrade presents a unique opportunity for an innovative nuclear physics program, which seamlessly integrates a rich historical background with a promising future. The proposed physics program encompass a diverse range of investigations centered around the nonperturbative dynamics inherent in hadron structure and the exploration of strongly interacting systems. It builds upon the exceptional capabilities of CEBAF in high-luminosity operations, the availability of existing or planned Hall equipment, and recent advancements in accelerator technology. The proposed program cover various scientific topics, including Hadron Spectroscopy, Partonic Structure and Spin, Hadronization and Transverse Momentum, Spatial Structure, Mechanical Properties, Form Factors and Emergent Hadron Mass, Hadron-Quark Transition, and Nuclear Dynamics at Extreme Conditions, as well as QCD Confinement and Fundamental Symmetries. Each topic highlights the key measurements achievable at a 22 GeV CEBAF accelerator. Furthermore, this document outlines the significant physics outcomes and unique aspects of these programs that distinguish them from other existing or planned facilities. In summary, this document provides an exciting rationale for the energy upgrade of CEBAF to 22 GeV, outlining the transformative scientific potential that lies within reach, and the remarkable opportunities it offers for advancing our understanding of hadron physics and related fundamental phenomena.

nucl-ex↗
arXiv2023

Measurement of the $e^{+}e^{-}\rightarrowωπ^{0}π^{0}$ cross section at center-of-mass energies from 2.0 to 3.08 GeV

The cross section of the process $e^{+}e^{-}\toωπ^{0}π^{0}$ is measured at nineteen center-of-mass energies from 2.0 to 3.08 GeV using data collected with the BESIII detector at the BEPCII storage ring. A resonant structure around 2.20 GeV is observed with statistical significance larger than $5σ$. Using a coherent fit to the cross section line shape, the mass and width are determined to be $M=2222\pm7\pm2~{\rm MeV}/c^2$ and $\varGamma=59\pm30\pm6~{\rm MeV}$, respectively, where the first uncertainties are statistical and the second ones are systematic.

hep-ex↗
arXiv2023

Measurement of the absolute branching fraction of the inclusive decay $\barΛ_{c}^{-} \to \bar{n} + X$

Based on $e^+e^-$ collision data corresponding to an integrated luminosity of 4.5 $fb^{-1}$ collected at the center-of-mass energies between 4.600 and 4.699 GeV with the BESIII detector at BEPCII, the absolute branching fraction of the inclusive decay $Λ^{+}_{c}\to n + X$, where $X$ refers to any possible final state particles, is measured. The absolute branching fraction is determined to be $\mathcal{B}(Λ^{+}_{c}\to n + X) = (32.4 \pm 0.7 \pm 1.5)\% $, where the first uncertainty is statistical and the second systematic. Assuming $CP$ symmetry, the measurement indicates that about one-fourth of $Λ^{+}_{c}$ ($\barΛ_{c}^-$) decay modes with a neutron (an anti-neutron) in the final state have not been observed.

hep-ex↗
arXiv2023

Measurement of the absolute branching fraction of the inclusive decay $D_s^+\to π^+π^+π^- X$

Using an $e^+ e^-$ collision data sample with a total integrated luminosity of $3.19$ fb$^{-1}$ collected with the BESIII detector at a center-of-mass energy of 4.178 GeV, the branching fraction of the inclusive decay of the $D_s^+$ meson to final states including at least three charged pions is measured for the first time to be ${\cal B}(D_s^+\toπ^+ π^+ π^- X) = (32.81 \pm 0.35_{\rm stat} \pm {0.63_{\rm syst}})\%$. In this measurement the charged pions from $K_S^0$ meson decays are excluded. The partial branching fractions of $D_s^+\toπ^+ π^+ π^- X$ are also measured as a function of the $π^+ π^+ π^-$ invariant mass.

hep-ex↗
arXiv2023

Measurement of the $C\!P$-even fraction of $D^0\to K^+K^-π^+π^-$

A determination of the $C\!P$-even fraction $F_+$ in the decay $D^0 \to K^+K^-π^+π^-$ is presented. Using $2.93$ fb$^{-1}$ of $e^+e^-\toψ(3770)\to D\bar{D}$ data collected by the BESIII detector, one charm meson is reconstructed in the signal mode and the other in a $C\!P$ eigenstate or the decay $D\to K_{S, L}^0π^+π^-$. Analysis of the relative rates of these double-tagged events yields the result $F_+ = 0.730 \pm 0.037 \pm 0.021$, where the first uncertainty is statistical and the second is systematic. This is the first model-independent measurement of $F_+$ in $D^0 \to K^+K^-π^+π^-$ decays.

hep-ex↗
arXiv2023

Ambiguities in Partial Wave Analysis of Two Spinless Meson Photoproduction

We describe the formalism to analyze the mathematical ambiguities arising in partial-wave analysis of two spinless mesons produced with a linearly polarized photon beam. We show that partial waves are uniquely defined when all accessible observables are considered, for a wave set which includes $S$ and $D$ waves. The inclusion of higher partial waves does not affect our results, and we conclude that there are no mathematical ambiguities in partial-wave analysis of two mesons produced with a linearly polarized photon beam. We present Monte Carlo simulations to illustrate our results.

hep-ph↗
arXiv2023

Measurements of Differential Cross Sections of Inclusive $π^0$ and $K^0_S$ Production in $e^{+}e^{-}$ Annihilation at Energies from 2.2324 to 3.6710 GeV

Based on electron positron collision data collected with the BESIII detector operating at the BEPCII storage rings, the differential cross sections of inclusive $π^0$ and $K^0_S$ production as a function of hadron momentum, normalized by the total cross section of the $e^{+}e^{-} \to$ hadrons process, are measured at six center-of-mass energies from 2.2324 to 3.6710 GeV. Our results with a relative hadron energy coverage from 0.1 to 0.9 significantly deviate from several theoretical calculations based on existing fragmentation functions, especially at lower energies.

hep-ex↗
arXiv2023

Measurement of Branching Fractions of Singly Cabibbo-suppressed Decays $Λ_c^+ \rightarrow Σ^{0} K^+$ and $Σ^{+} K_{S}^0$

Based on a sample of 4.4 $\mathrm{fb}^{-1}$ of $e^{+}e^{-}$ annihilation data collected in the energy region between 4.6 GeV and 4.7 GeV with the BESIII detector at BEPCII, two singly Cabibbo-suppressed decays $Λ_c^+ \rightarrow Σ^0 K^+$ and $Λ_{c}^{+} \rightarrow Σ^+ K_{S}^0$ are studied. The ratio of the branching fraction $\mathcal{B}(Λ_c^+ \rightarrow Σ^0 K^+)$ relative to $\mathcal{B}(Λ_c^+ \rightarrow Σ^0 π^+)$ is measured to be $0.0361 \pm 0.0073(\mathrm{stat.}) \pm 0.0005(\mathrm{syst.})$, and the ratio of $\mathcal{B}(Λ_c^+ \rightarrow Σ^+ K_{S}^0)$ relative to $\mathcal{B}(Λ_{c}^{+} \rightarrow Σ^+ π^+ π^-)$ is measured to be $0.0106 \pm 0.0031(\mathrm{stat.}) \pm 0.0004(\mathrm{syst.})$. After taking the world-average branching fractions of the reference decay channels, the branching fractions $\mathcal{B}(Λ_c^+ \rightarrow Σ^0 K^+)$ and $\mathcal{B}(Λ_{c}^{+} \rightarrow Σ^+ K_{S}^0)$ are determined to be $(4.7\pm 0.9(\mathrm{stat.})\pm 0.1(\mathrm{syst.}) \pm 0.3(\mathrm{ref.}))\times10^{-4}$ and $(4.8\pm 1.4(\mathrm{stat.})\pm 0.2(\mathrm{syst.}) \pm 0.3(\mathrm{ref.}))\times10^{-4}$, respectively. The branching fraction of the $Λ_{c}^{+} \rightarrow Σ^+ K_{S}^0$ decay is measured for the first time.

hep-ex↗
arXiv2023

Evidence for $η_c$(2S)$\to\pipieta$ decay

The decay $η_c(2S)\to\pipieta$ is searched for through the radiative transition $ψ(3686) \toγη_c(2S)$ using 448 million $ψ$(3686) events accumulated at the BESIII detector. The first evidence of $η_c(2S)\toπ^+π^-η$ is found with a statistical significance of 3.5$σ$. The product of the branching fractions of $ψ(3686)\toγη_c(2S)$ and $η_c(2S)\to\pipieta$ is measured to be $Br(ψ(3686)\toγη_c(2S))\times Br(η_c(2S)\to\pipieta)=(2.97\pm0.81\pm0.26)\times10^{-6}$, where the first uncertainty is statistical and the second one is systematic. The branching fraction of the decay $η_c(2S)\to\pipieta$ is determined to be $Br(η_c(2S)\to\pipieta)=(42.4\pm11.6\pm3.8\pm30.3)\times10^{-4}$, where the third uncertainty is transferred from the uncertainty of the branching fraction of $ψ(3686)\toγη_c(2S)$.

hep-ex↗
arXiv2023

Long-lasting XUV activation of helium nanodroplets for avalanche ionization

We study the dynamics of avalanche ionization of pure helium nanodroplets activated by a weak extreme-ultraviolet (XUV) pulse and driven by an intense near-infrared (NIR) pulse. In addition to a transient enhancement of ignition of a nanoplasma at short delay times $\sim200$~fs, long-term activation of the nanodroplets lasting up to a few nanoseconds is observed. Molecular dynamics simulations suggest that the short-term activation is caused by the injection of seed electrons into the droplets by XUV photoemission. Long-term activation appears due to electrons remaining loosely bound to photoions which form stable `snowball' structures in the droplets. Thus, we show that XUV irradiation can induce long-lasting changes of the strong-field optical properties of nanoparticles, potentially opening new routes to controlling avalanche-ionization phenomena in nanostructures and condensed-phase systems.

physics.atm-clus↗
arXiv2023

Observation of a New $X(3872)$ Production Process $e^+e^-\toωX(3872)$

Using $4.7~\rm fb^{-1}$ of $e^+e^-$ collision data at center-of-mass energies from 4.661 to 4.951 GeV collected by the BESIII detector at the BEPCII collider, we observe the $X(3872)$ production process $e^{+}e^{-}\toωX(3872)$ for the first time. The significance is $7.8σ$, including both the statistical and systematic uncertainties. The $e^+e^-\toωX(3872)$ Born cross section and the corresponding upper limit at 90\% confidence level at each energy point are reported. The line shape of the cross section indicates that the $ωX(3872)$ signals may be from the decays of some non-trivial structures.

hep-ex↗
arXiv2023

Observation of the $Y(4230)$ and evidence for a new vector charmonium-like state $Y(4710)$ in $e^{+}e^{-}\to K_{S}^{0} K_{S}^{0} J/ψ$

Cross sections for the process $e^{+} e^{-} \to K_{S}^{0} K_{S}^{0} J/ψ$ at center-of-mass energies from $4.128$ to $4.950$ GeV are measured using data samples with a total integrated luminosity of 21.2 fb$^{-1}$ collected by the BESIII detector operating at the BEPCII storage ring. The $Y(4230)$ state is observed in the energy dependence of the $e^{+} e^{-} \to K_{S}^{0} K_{S}^{0} J/ψ$ cross section for the first time with a statistical significance of 26.0$σ$. In addition, an enhancement around $4.710$ GeV, called the $Y(4710)$, is seen with a statistical significance of 4.2$σ$. There is no clear structure around $4.484$ GeV. Using a fit with a coherent sum of three Breit-Wigner functions, we determine the mass and width of the $Y(4230)$ state to be $4226.9 \pm 6.6 \pm 21.9$ MeV/$c^{2}$ and $71.7 \pm 16.2 \pm 31.4$ MeV, respectively, and the mass and width of the $Y(4710)$ state to be $4704.0 \pm 52.3 \pm 69.5$ MeV/$c^{2}$ and $183.2 \pm 114.0 \pm 90.8$ MeV, respectively, where the first uncertainties are statistical and the second are systematic. In addition, the average Born cross section ratio of $e^{+} e^{-} \to K_{S}^{0} K_{S}^{0} J/ψ$ to $e^{+} e^{-} \to K^{+} K^{-} J/ψ$ is measured to be $0.388_{-0.028}^{+0.035}\pm0.016$, or $0.426_{-0.031}^{+0.038}\pm0.018$ if three-body phase space is considered.

hep-ex↗
arXiv2023

Study of the $h_c$($1^1P_1$) meson via $ψ(2S) \rightarrow π^0 h_c$ decays at BESIII

Using 448 million $ψ(2S)$ events, the spin-singlet $P$-wave charmonium state $h_c$(1$^1P_1$) is studied via the $ψ(2S) \rightarrow π^0 h_c$ decay followed by the $h_c \to γη_c$ transition. The branching fractions are measured to be $\mathcal{B}_{\rm Inc}(ψ(2S) \rightarrow π^0h_c) \times \mathcal{B}_{\rm Tag}(h_c \rightarrow γη_c) = (4.22 ^{+0.27}_{-0.26} \pm 0.19) \times 10^{-4}$ , $\mathcal{B}_{\rm Inc}(ψ(2S) \rightarrow π^0h_c) = (7.32 \pm 0.34 \pm 0.41) \times 10^{-4}$, and $\mathcal{B}_{\rm Tag}(h_c \rightarrow γη_c) = (57.66 ^{+3.62}_{-3.50} \pm 0.58)\%$, where the uncertainties are statistical and systematic, respectively. The $h_c$(1$^1P_1$) mass and width are determined to be $M = (3525.32 \pm 0.06 \pm 0.15)~\rm{MeV}/c^{\rm{2}}$ and ${\mathit Γ} = (0.78 ^{+0.27}_{-0.24} \pm 0.12)~\rm{MeV}$. Using the center of gravity mass of the three $χ_{cJ}$(1$^3 P_J$) mesons ($M(\rm c.o.g.)$), the $1P$ hyperfine mass splitting is estimated to be $Δ_{\rm hyp} = M(h_c) - M(\rm c.o.g.) = (0.03 \pm 0.06 \pm 0.15) ~ \rm{MeV}/c^{\rm{2}}$, which is consistent with the expectation that the $1P$ hyperfine splitting is zero at the lowest-order.

hep-ex↗
arXiv2023

Improved measurement of the absolute branching fraction of inclusive semileptonic $Λ_c^+$ decay

Using $4.5 \mathrm{fb}^{-1}$ of $e^+e^-$ annihilation data samples collected at center-of-mass energies ranging from 4.600 to 4.698 GeV with the BESIII detector at the BEPCII collider, we measured the absolute branching fraction for the inclusive semileptonic decay $Λ_c^+\rightarrow Xe^+ν_e$, where $X$ refers to any possible particle system. The branching fraction of the decay is determined to be $\mathcal{B}({\it Λ}^+_c\rightarrow Xe^+ν_e)=(4.06\pm0.10_{\rm stat.}\pm0.09_{\rm syst.})\%$. Our result improves the precision of previous measurement of $\mathcal{B}({\it Λ}^+_c\rightarrow Xe^+ν_e)$ by more than threefold. Using the known $Λ_c^+$ lifetime and the charge-averaged semileptonic decay width of nonstrange charmed mesons, we measure the ratio of inclusive semileptonic decay widths $Γ(Λ_c^+\rightarrow X e^+ν_e)/\barΓ(D\rightarrow Xe^+ν_e)=1.28\pm0.05$, where statistical and systematic uncertainties are combined.

hep-ex↗
arXiv2023

Study of the $e^+e^- \to π^{+}π^{-}ω$ process at center-of-mass energies between 4.0 and 4.6 GeV

Using $15.6$ $\rm fb^{-1}$ of $e^+e^-$ collision data collected at twenty-four center-of-mass energies from $4.0$ to $4.6$ GeV with the BESIII detector, the helicity amplitudes of the process $e^+e^-\to π^{+}π^{-}ω$ are analyzed for the first time. Born cross section measurements of two-body intermediate resonance states with statistical significance greater than 5$σ$ are presented, such as $f_{0}(500)$, $f_{0}(980)$, $f_{2}(1270)$, $f_{0}(1370)$, $b_{1}(1235)^{\pm}$, and $ρ(1450)^{\pm}$. In addition, evidence of a resonance state in $e^+e^-\to π^+π^-ω$ production is found. The mass of this state obtained by line shape fitting is about 4.2 GeV/$c^2$, which is consistent with the production of $ψ(4160)$ or $Y(4220)$.

hep-ex↗
arXiv2023

Helicity amplitude analysis of $χ_{cJ} \rightarrow ϕϕ$

Using (447.9 $\pm$ 2.3) million $ψ$(3686) events collected with the BESIII detector, the decays of $χ_{cJ} \rightarrow ϕϕ$ ($J$=0, 1, 2) have been studied via the decay $ψ(3686)\rightarrowγχ_{cJ}$. The branching fractions of the decays $χ_{cJ} \rightarrow ϕϕ$ ($J$=0, 1, 2) are determined to be $(8.48\pm0.26\pm0.27)\times10^{-4}$, $(4.36\pm0.13\pm0.18)\times10^{-4}$, and $(13.36\pm0.29\pm0.49)\times10^{-4}$, respectively, which are the most precise measurements to date. From a helicity amplitude analysis of the process $ψ(3686) \rightarrow γχ_{cJ}, χ_{cJ}\rightarrow ϕϕ, ϕ\rightarrow K^{+}K^{-}$, the polarization parameters of the $χ_{cJ} \rightarrow ϕϕ$ decays are determined for the first time.

hep-ex↗
arXiv2023

Study of $e^+e^-\rightarrowΩ^{-}\barΩ^{+}$ at center-of-mass energies from 3.49 to 3.67 GeV

Using data samples of $e^+e^-$ collisions collected with the BESIII detector at eight center-of-mass energy points between 3.49 and 3.67 GeV, corresponding to an integrated luminosity of 670 pb$^{-1}$, we present the upper limits of Born cross sections and the effective form factor for the process $e^+e^-\rightarrowΩ^{-}\barΩ^{+}$. A fit to the cross sections using a pQCD-derived energy dependent function shows no significant threshold effect. The upper limit on the measured effective form factor is consistent with a theoretical prediction within the uncertainty of 1$σ$. These results provide new experimental information on the production mechanism of $Ω$.

hep-ex↗