arXiv subjects

K Fischer

Publications and source records attributed to K Fischer.

At least 55 records · Page 3Linked to original sources

arXiv2023

Study of the decay $J/ψ\to ϕπ^{0}η$

Based on $(10.09 \pm 0.04) \times 10^9$ $J/ψ$ events collected with the BESIII detector operating at the BEPCII collider, a partial wave analysis of the decay $J/ψ\to ϕπ^{0}η$ is performed. We observe for the first time two new structures on the $ϕη$ invariant mass distribution, with statistical significances of $24.0σ$ and $16.9σ$; the first with $J^{\rm PC}$ = $1^{+-}$, mass M = (1911 $\pm$ 6 (stat.) $\pm$ 14 (sys.))~MeV/$c^{2}$, and width $Γ= $ (149 $\pm$ 12 (stat.) $\pm$ 23 (sys.))~MeV, the second with $J^{\rm PC}$ = $1^{--}$, mass M = (1996 $\pm$ 11 (stat.) $\pm$ 30 (sys.))~MeV/$c^{2}$, and width $Γ$ = (148 $\pm$ 16 (stat.) $\pm$ 66 (sys.))~MeV. These measurements provide important input for the strangeonium spectrum. In addition, the $f_0(980)-a_0(980)^0$ mixing signal in $J/ψ\to ϕf_0(980) \to ϕa_0(980)^0$ and the corresponding electromagnetic decay $J/ψ\to ϕa_0(980)^0$ are measured with improved precision, providing crucial information to understand the nature of $a_0(980)^0$ and $f_0(980)$.

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arXiv2023

Precision Measurements of $D_s^+ \to ηe^+ ν_e$ and $D_s^+ \to η^\prime e^+ ν_e$

Precision measurements of the semileptonic decays $D_s^+ \to ηe^+ ν_e$ and $D_s^+ \to η^\prime e^+ ν_e$ are performed with 7.33\,fb$^{-1}$ of $e^+e^-$ collision data collected at center-of-mass energies between 4.128 and 4.226 GeV with the BESIII detector. The branching fractions obtained are $\mathcal{B}(D_s^+ \to ηe^{+} ν_e)$ = $(2.255\pm0.039_{\rm stat}\pm 0.051_{\rm syst})\%$ and $\mathcal{B}(D_s^+ \to η^{\prime} e^{+} ν_e)$ = $(0.810\pm0.038_{\rm stat}\pm 0.024_{\rm syst})\%$. Combining these results with the $\mathcal{B}(D^+\toηe^+ ν_e)$ and $\mathcal{B}(D^+\toη^\prime e^+ ν_e)$ obtained from previous BESIII measurements, the $η-η^\prime$ mixing angle in the quark flavor basis is determined to be $ϕ_{\rm P} = (40.0\pm2.0_{\rm stat}\pm0.6_{\rm syst})^\circ$. Moreover, from the fits to the partial decay rates of $D_s^+ \to ηe^+ ν_e$ and $D_s^+ \to η^\prime e^+ ν_e$, the products of the hadronic transition form factors $f_+^{η^{(\prime)}}(0)$ and the modulus of the $c\to s$ Cabibbo-Kobayashi-Maskawa matrix element $|V_{cs}|$ are determined by using different hadronic transition form factor parametrizations. Based on the two-parameter series expansion, the products $f^η_+(0)|V_{cs}| = 0.4519\pm0.0071_{\rm stat}\pm0.0065_{\rm syst}$ and $f^{η^\prime}_+(0)|V_{cs}| = 0.525\pm0.024_{\rm stat}\pm0.009_{\rm syst}$ are extracted. All results determined in this work supersede those measured in the previous BESIII analyses based on the 3.19 fb$^{-1}$ subsample of data at 4.178 GeV.

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arXiv2023

Observation of the hindered electromagnetic Dalitz decay $ψ(3686) \to e^+ e^- η_c$

Using a data sample of $(448.1 \pm 2.9)\times10^6 ~ψ(3686)$ decays collected at an $e^+ e^-$ center-of-mass energy of $3.686~\rm{GeV}$ by the BESIII detector at BEPCII, we report an observation of the hindered electromagnetic Dalitz decay $ψ(3686) \to e^+ e^- η_c$ with a significance of $7.9σ$. The branching fraction is determined to be $\mathcal{B} (ψ(3686) \to e^+ e^- η_c) = (3.77 \pm 0.40_{\rm stat.} \pm 0.18_{\rm syst.})\times 10^{-5}$, agreeing well with the prediction of the vector meson dominance model. This is the first measurement of the electromagnetic Dalitz transition between the $ψ(3686)$ and the $η_c$, which provides new insight into the electromagnetic properties of this decay, and offers new opportunities to measure the absolute branching fractions of $η_c$ decays.

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arXiv2023

Study of $e^+e^-\toηϕ$ at center-of-mass energies from 3.773 to 4.600 GeV

We present a study of the process $e^{+}e^{-}\toηϕ$ using data samples collected with the BESIII detector corresponding to an integrated luminosity of 15.03 fb$^{-1}$ at 23 center-of-mass energies from 3.773 to 4.600 GeV. The Born cross sections are measured at each energy and a coherent fit to cross-section lineshape is performed using a Breit-Wigner parametrization to search for charmonium-like vector states. No significant signals of the $Y(4230)$ and $Y(4360)$ resonances are observed.

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arXiv2023

Observation of the $ψ(3686)$ decays into $Σ^{+}\barΣ^{-}ω$ and $Σ^{+}\barΣ^{-}{\mathcalϕ}$

Based on $(27.08\pm 0.14)\times10^{8}$ $ψ(3686)$ events collected with the BESIII detector operating at the BEPCII collider, the $ψ(3686)\toΣ^{+}\barΣ^{-}ω$ and $Σ^{+}\barΣ^{-}ϕ$ decays are observed for the first time with statistical significances of 13.8$σ$ and 7.6$σ$, respectively. The corresponding branching fractions are measured to be $\mathcal{B}(ψ(3686)\toΣ^{+}\barΣ^{-}ω)=(1.90 \pm 0.18 \pm 0.21) \times 10^{-5}$ and $\mathcal{B}(ψ(3686)\toΣ^{+}\barΣ^{-}ϕ)=(2.96 \pm 0.54 \pm 0.41) \times 10^{-6}$, where the first uncertainties are statistical and the second systematic.

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arXiv2023

Measurement of the branching fractions of the singly Cabibbo-suppressed decays $Λ_{c}^{+}\to pη$ and $Λ_{c}^{+}\to pω$

Based on 4.5 $\mbox{fb$^{-1}$}$ $e^{+}e^{-}$ collision data collected with BESIII detector at seven energy points between 4.600 and 4.699 GeV, the branching fractions for $Λ_{c}^{+}\to pη$ and $Λ_{c}^{+}\to pω$ were measured by means of single-tag method. The branching fractions of $Λ_{c}^{+}\to pη$ and $Λ_{c}^{+}\to pω$ are determined to be $(1.57\pm0.11_{\rm {stat}}\pm0.04_{\rm{syst}})\times10^{-3}$ and $(1.11\pm0.20_{\rm{stat}}\pm0.07_{\rm{syst}})\times10^{-3}$, with a statistical significance of greater than 10 $σ$ and 5.7 $σ$, respectively. These results are consistent with the previous measurements by BESIII, LHCb and Belle, and the result of $Λ_{c}^{+}\to pη$ is the most precise to date.

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arXiv2023

Search for $J/ψ$ weak decays containing $D$ meson

Using a sample of about 10 billion $J/ψ$ events with the BESIII detector, we search for the weak decays of $J/ψ\to \bar{D}^0π^0 + c.c.$, $J/ψ\to \bar{D}^0η+ c.c.$, $J/ψ\to \bar{D}^0ρ^0 + c.c.$, $J/ψ\to D^-π^+ + c.c.$, and $J/ψ\to D^-ρ^+ + c.c.$. Since no significant signal is observed, we set the upper limits of the branching fractions of these decays to be $\mathcal{B}(J/ψ\to \bar{D}^0π^0 + c.c.) < 4.7 \times 10^{-7}$, $\mathcal{B}(J/ψ\to \bar{D}^0η+ c.c.) < 6.8 \times 10^{-7}$, $\mathcal{B}(J/ψ\to \bar{D}^0ρ^0 + c.c.) < 5.2 \times 10^{-7}$, $\mathcal{B}(J/ψ\to D^-π^+ + c.c.) < 7.0 \times 10^{-8}$, and $\mathcal{B}(J/ψ\to D^-ρ^+ + c.c.) < 6.0 \times 10^{-7}$ at the 90\% confidence level.

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arXiv2023

Measurement of $e^{+}e^{-}\rightarrowηJ/ψ$ Cross Section from $\sqrt{s}=$ 3.808 GeV to 4.951 GeV

Using data samples with an integrated luminosity of 22.42 fb$^{-1}$ collected by the BESIII detector operating at the BEPCII storage ring, we measure the cross sections of the $e^{+}e^{-}\rightarrow\etaJ/ψ$ process at center-of-mass energies from 3.808 to 4.951 GeV. Three structures are observed in the line shape of the measured cross sections. A maximum-likelihood fit with $ψ(4040)$, two additional resonances, and a non-resonant component is performed. The mass and width of the first additional state are $(4219.7\pm2.5\pm4.5) \rm{MeV}/\rm{c}^2$ and $(80.7\pm4.4\pm1.4) \rm{MeV}$, respectively, consistent with the $ψ(4230)$. For the second state, the mass and width are $(4386\pm13\pm17) \rm{MeV}/\rm{c}^2$ and $(177\pm32\pm13) \rm{MeV}$, respectively, consistent with the $ψ(4360)$. The first uncertainties are statistical and the second ones are systematic. The statistical significance of $ψ(4040)$ is $8.0σ$ and those for $ψ(4230)$ and $ψ(4360)$ are more than $10.0σ$.

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arXiv2023

Observation of $J/ψ$ decays to $e^{+}e^{-}e^{+}e^{-}$ and $e^{+}e^{-}μ^{+}μ^{-}$

Using a data sample of $4.481\times 10^8 ψ^\prime$ events collected with the BESIII detector, we report the first observation of the four-lepton-decays $J/ψ\to e^+e^-e^+e^-$ and $J/ψ\to e^+e^-μ^+μ^-$ utilizing the process $ψ^\prime\to π^+π^- J/ψ$. The branching fractions are determined to be $[5.48\pm0.31~(\rm stat)\pm0.45~(\rm syst)]\times 10^{-5}$ and $[3.53~\pm0.22~(\rm stat)\pm0.13~(\rm syst)]\times 10^{-5}$, respectively. The results are consistent with theoretical predictions. No significant signal is observed for $J/ψ\to μ^+μ^-μ^+μ^-$, and an upper limit on the branching fraction is set at $1.6\times 10^{-6}$ at the 90$\%$ confidence level. A CP asymmetry observable is constructed for the first two channels, which is measured to be $(-0.012\pm0.054\pm0.010)$ and $(0.062\pm0.059\pm0.006)$, respectively. No evidence for CP violation is observed in this process.

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arXiv2023

Measurements of the absolute branching fractions of $Ω^-$ decays and test of the $ΔI = 1/2$ rule

Based on a data set of $(27.12\pm0.10)\times 10^8$ $ψ(3686)$ events collected at the BESIII experiment, the absolute branching fractions of the three dominant $Ω^-$ decays are measured to be $\mathcal{B}_{Ω^- \to Ξ^0 π^-} = (25.03\pm0.44\pm0.53)\%$, $\mathcal{B}_{Ω^- \to Ξ^- π^0} = (8.43\pm0.52\pm0.28)\%$, and $\mathcal{B}_{Ω^- \to ΛK^-} = (66.3\pm0.8\pm2.0)\%$, where the first and second uncertainties are statistical and systematic, respectively. The ratio between $\mathcal{B}_{Ω^- \to Ξ^0 π^-}$ and $\mathcal{B}_{Ω^- \to Ξ^- π^0}$ is determined to be $2.97\pm0.19\pm0.11$, which is in good agreement with the PDG value of $2.74\pm0.15$, but greater by more than four standard deviations than the theoretical prediction of 2 obtained from the $ΔI = 1/2$ rule.

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arXiv2023

Measurement of $e^{+}e^{-}\toϕη'$ cross sections at center-of-mass energies from 3.508 to 4.951 GeV and search for the decay $ψ(3770)\toϕη'$

The cross sections of the $e^{+}e^{-}\toϕη'$ process at center-of-mass energies from 3.508 to 4.951 GeV are measured with high precision using 26.1 fb$^{-1}$ data collected with the BESIII detector operating at the BEPCII storage ring. The cross sections are of the order of a few picobarn, and decrease as the center-of-mass energy increases as $s^{-n/2}$ with $n=4.35\pm 0.14$. This result is in agreement with the Nambu-Jona-Lasinio model prediction of $n=3.5\pm 0.9$. In addition, the charmless decay $ψ(3770)\toϕη'$ is searched for by fitting the measured cross sections, yet no significant signal is observed. The upper limit of ${\cal B}(ψ(3770)\toϕη')$ at the 90\% confidence level is determined to be $2.3\times 10^{-5}$.

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arXiv2023

Search for the semileptonic decays $D^+_s \to K_1(1270)^0 e^+ν_e$ and $D^+_s \to b_1(1235)^0 e^+ν_e$

By analyzing 7.33\,fb$^{-1}$ of $e^+e^-$ collision data collected at center-of-mass energies between 4.128 and 4.226 GeV with the BESIII detector, we search for the semileptonic decays $D^+_s \to K_1(1270)^0 e^+ν_e$ and $D^+_s \to b_1(1235)^0 e^+ν_e$ for the first time. No significant signals are observed for either decay mode. The upper limits on the (product) branching fractions are determined to be ${\mathcal B}[D^+_s \to K_1(1270)^0 e^+ν_e] < 4.1\times 10^{-4}$ and ${\mathcal B}[D^+_s \to b_1(1235)^0 e^+ν_e]\cdot {\mathcal B}[b_1(1235)^0\to ωπ^0] < 6.4\times 10^{-4}$ at 90\% confidence level.

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arXiv2023

Novel method to extract the femtometer structure of strange baryons using the vacuum polarization effect

One of the fundamental goals of particle physics is to gain microscopic understanding of the strong interaction. Electromagnetic form factors quantify the structure of hadrons in terms of charge and magnetization distributions. While the nucleon structure has been investigated extensively, data on hyperons is still scarce. It has recently been demonstrated that electron-positron annihilations into hyperon-antihyperon pairs provide a powerful tools to investigate their inner structure. We present a novel method useful for hyperon-antihyperon pairs of different types which exploits the cross section enhancement due to the vacuum polarization effect at the $J/ψ$ resonance. Using the 10 billion $J/ψ$ events collected with the BESIII detector, this allows a thorough determination of the hyperon structure . The result is essentially a precise snapshot of a $\barΛΣ^0$~($Λ\barΣ^0$) pair in the making, encoded in the form factor ratio and the phase. Their values are measured to be $R = 0.860\pm0.029({\rm stat.})\pm0.010({\rm syst.})$, $ΔΦ_1=(1.011\pm0.094({\rm stat.})\pm0.010({\rm syst.}))~\rm rad$ for $\barΛΣ^0$ and $ΔΦ_2=(2.128\pm0.094({\rm stat.})\pm0.010({\rm syst.}))~\rm rad$ for $Λ\barΣ^0$, respectively. Furthermore, charge-parity (CP) breaking is investigated for the first time in this reaction and found to be consistent with CP symmetry.

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arXiv2023

Search for a scalar partner of the $X(3872)$ via $ψ(3770)$ decays into $γηη'$ and $γπ^{+}π^{-}J/ψ$

Using a data sample corresponding to an integrated luminosity of 2.93 fb$^{-1}$ collected at a center-of-mass energy of 3.773~GeV with the BESIII detector at the BEPCII collider, we search for a scalar partner of the $X(3872)$, denoted as $X(3700)$, via $ψ(3770)\to γηη'$ and $γπ^{+}π^{-}J/ψ$ processes. No significant signals are observed and the upper limits of the product branching fractions $ {\cal B}(ψ(3770)\toγX(3700))\cdot {\cal B}(X(3700)\to ηη')$ and ${\cal B}(ψ(3770)\toγX(3700))\cdot {\cal B}(X(3700)\toπ^{+}π^{-}J/ψ)$ are determined at the 90\% confidence level, for the narrow $X(3700)$ with a mass ranging from 3710 to 3740 MeV/$c^2$, which are from 0.8 to 1.8 $(\times 10^{-5})$ and 0.9 to 3.4 $(\times 10^{-5})$, respectively.

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arXiv2023

A coupled-channel analysis of the $X(3872)$ lineshape with BESIII data

We perform a study of the $X(3872)$ lineshape using the data samples of $e^+e^-\toγX(3872)$, $X(3872)\to D^0\bar{D}^0 π^0$ and $π^+π^- J/ψ$ collected with the BESIII detector. The effects of the coupled-channels and the off-shell $D^{*0}$ are included in the parameterization of the lineshape. The lineshape mass parameter is obtained to be $M_{X}=(3871.63\pm 0.13^{+0.06}_{-0.05})$ MeV. Two poles are found on the first and second Riemann sheets corresponding to the $D^{*0}\bar{D}^0$ branch cut. The pole location on the first sheet is much closer to the $D^{*0}\bar{D}^0$ threshold than the other, and is determined to be $7.04\pm0.15^{+0.07}_{-0.08}$ MeV above the $D^0\bar{D}^0π^0$ threshold with an imaginary part $-0.19\pm0.08^{+0.14}_{-0.19}$ MeV.

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arXiv2023

Observation of $χ_{cJ}\to Λ\bar Λη$

By analyzing $(448.1\pm2.9)\times10^6$ $ψ(3686)$ events collected with the BESIII detector operating at the BEPCII collider, the decays of $χ_{cJ} \to Λ\bar Λη$ ($J=0$, 1 and 2) are observed for the first time with statistical significances of $13.9σ$, $6.7σ$, and $8.2σ$, respectively. The product branching fractions of $ψ(3686)\toγχ_{cJ}$ and $χ_{cJ}\to Λ\bar Λη$ are measured. Dividing by the world averages of the branching fractions of $ψ(3686)\toγχ_{cJ}$, the branching fractions of $χ_{cJ}\to Λ\bar Λη$ decays are determined to be $(2.31\pm0.30\pm0.21)\times10^{-4}$, $(5.86\pm1.38\pm0.68)\times10^{-5}$, and $(1.05\pm0.21\pm0.15)\times10^{-4}$ for $J=0$, 1 and 2, respectively, where the first uncertainties are statistical and the second systematic.

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arXiv2023

Measurements of the branching fractions of the inclusive decays $D^{0}(D^{+})\to π^+π^+π^-X$

Using $e^+e^-$ annihilation data corresponding to an integrated luminosity of 2.93 fb$^{-1}$ taken at a center-of-mass energy of 3.773 GeV with the BESIII detector, we report the first measurements of the branching fractions of the inclusive decays $D^0\to π^+π^+π^-X$ and $D^+\to π^+π^+π^-X$, where pions from $K^0_S$ decays have been excluded from the $π^+π^+π^-$ system and $X$ denotes any possible particle combination. The branching fractions of $D^0(D^+)\to π^+π^+π^-X$ are determined to be ${\mathcal B}(D^0\to π^+π^+π^-X)=(17.60\pm0.11\pm0.22)\%$ and ${\mathcal B}(D^+\to π^+π^+π^-X)=(15.25\pm0.09\pm0.18)\%$, where the first uncertainties are statistical and the second systematic.

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arXiv2023

Measurement of branching fractions of $Λ_{c}^{+}$ decays to $Σ^{+} K^{+} K^{-}$, $Σ^{+}ϕ$ and $Σ^{+} K^{+} π^{-}(π^{0})$

Based on 4.5 fb$^{-1}$ data taken at seven center-of-mass energies ranging from 4.600 to 4.699 GeV with the BESIII detector at the BEPCII collider, we measure the branching fractions of $Λ_{c}^{+}\rightarrowΣ^{+}+hadrons$ relative to $Λ_{c}^{+}\rightarrow Σ^+ π^+ π^-$. Combining with the world average branching fraction of $Λ_{c}^{+}\rightarrow Σ^+ π^+ π^-$, their branching fractions are measured to be $(0.377\pm0.042\pm0.018\pm0.021)\%$ for $Λ_{c}^{+}\rightarrowΣ^{+} K^{+} K^{-}$, $(0.200\pm0.023\pm0.010\pm0.011)\%$ for $Λ_{c}^{+}\rightarrowΣ^{+} K^{+} π^{-}$, $(0.414\pm0.080\pm0.029\pm0.023)\%$ for $Λ_{c}^{+}\rightarrowΣ^{+}ϕ$ and $(0.197\pm0.036\pm0.008\pm0.011)\%$ for $Λ_{c}^{+}\rightarrowΣ^{+}K^{+} K^{-}$(non-$ϕ$). In all the above results, the first uncertainties are statistical, the second are systematic and the third are from external input of the branching fraction of $Λ_{c}^{+}\rightarrow Σ^+ π^+ π^-$. Since no signal for $Λ_{c}^{+}\rightarrowΣ^{+} K^{+} π^{-}π^{0}$ is observed, the upper limit of its branching fraction is determined to be 0.11\% at the 90$\%$ confidence level.

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