arXiv subjects

A. Amoroso

Publications and source records attributed to A. Amoroso.

At least 685 records · Page 38Linked to original sources

arXiv2019

Observation of the decay $X(3872) \to π^0 χ_{c1}(1P)$

Using a total of $9.0~\mathrm{fb}^{-1}$ of $e^+e^-$ collision data with center-of-mass energies between 4.15 and 4.30 GeV collected by the BESIII detector, we search for the processes $e^+e^-\to γX(3872)$ with $X(3872)\toπ^0χ_{cJ}$ for $J=0,1,2$. We report the first observation of $X(3872)\toπ^{0}χ_{c1}$, a new decay mode of the $X(3872)$, with a statistical significance of more than 5$σ$. Normalizing to the previously established process $e^+e^-\to γX(3872)$ with $X(3872)\toπ^+π^-J/ψ$, we find ${\cal B}(X(3872) \to π^0 χ_{c1})/{\cal B}(X(3872) \to π^+π^- J/ψ) = 0.88^{+0.33}_{-0.27}\pm0.10$, where the first error is statistical and the second is systematic. We set 90% confidence level upper limits on the corresponding ratios for the decays to $π^0χ_{c0}$ and $π^0χ_{c2}$ of 19 and 1.1, respectively.

hep-ex↗

arXiv2019

Observation of $D^+_s\rightarrow p\bar{n}$ and confirmation of its large branching fraction

The baryonic decay $D^+_s\rightarrow p\bar{n}$ is observed, and the corresponding branching fraction is measured to be $(1.21\pm0.10\pm0.05)\times10^{-3}$, where the first uncertainty is statistical and second systematic. The data sample used in this analysis was collected with the BESIII detector operating at the BEPCII $e^+e^-$ double-ring collider with a center-of-mass energy of 4.178~GeV and an integrated luminosity of 3.19~fb$^{-1}$. The result confirms the previous measurement by the CLEO Collaboration and is of greatly improved precision, which may deepen our understanding of the dynamical enhancement of the W-annihilation topology in the charmed meson decays.

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arXiv2019

Study of the $D^0\to K^-μ^+ν_μ$ dynamics and test of lepton flavor universality with $D^0\to K^-\ell^+ν_\ell$ decays

Using $e^+e^-$ annihilation data of $2.93~\mathrm{fb}^{-1}$ collected at center-of-mass energy $\sqrt{s}=3.773$ GeV with the BESIII detector, we measure the absolute branching fraction of $D^{0}\to K^{-}μ^{+}ν_μ$ with significantly improved precision: ${\mathcal B}_{D^{0}\to K^{-}μ^{+}ν_μ}=(3.413\pm0.019_{\rm stat.}\pm0.035_{\rm syst.})\%$. Combining with our previous measurement of ${\mathcal B}_{D^0\to K^-e^+ν_e}$, the ratio of the two branching fractions is determined to be ${\mathcal B}_{D^0\to K^-μ^+ν_μ}/{\mathcal B}_{D^0\to K^-e^+ν_e}=0.974\pm0.007_{\rm stat.}\pm0.012_{\rm syst.}$, which agrees with the theoretical expectation of lepton flavor universality within the uncertainty. A study of the ratio of the two branching fractions in different four-momentum transfer regions is also performed, and no evidence for lepton flavor universality violation is found with current statistics. Taking inputs from global fit in the standard model and lattice quantum chromodynamics separately, we determine $f_{+}^{K}(0)=0.7327\pm0.0039_{\rm stat.}\pm0.0030_{\rm syst.}$ and $|V_{cs}| = 0.955\pm0.005_{\rm stat.}\pm0.004_{\rm syst.}\pm0.024_{\rm LQCD}$.

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arXiv2018

Observation of $D^{0(+)}\to K^0_Sπ^{0(+)}η^\prime$ and improved measurement of $D^0\to K^-π^+η^\prime$

By analyzing $2.93\ \rm fb^{-1}$ of data taken at a center-of-mass energy of 3.773~GeV with the BESIII detector, we measure the branching fractions of the Cabibbo-favored hadronic decays $D^0\to K^-π^+η^\prime$, $D^0\to K^0_Sπ^0η^\prime$ and $D^+\to K^0_Sπ^+η^\prime$, which are determined to be $(6.43 \pm 0.15_{\rm stat.} \pm 0.31_{\rm syst.})\times 10^{-3}$, $(2.52 \pm 0.22_{\rm stat.} \pm 0.15_{\rm syst.})\times 10^{-3}$ and $(1.90 \pm 0.17_{\rm stat.} \pm 0.13_{\rm syst.})\times 10^{-3}$, respectively. The precision of the branching fraction of $D^0\to K^-π^+η^\prime$ is significantly improved, and the processes $D^0\to K^0_Sπ^0η^\prime$ and $D^+\to K^0_Sπ^+η^\prime$ are observed for the first time.

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arXiv2018

Observation of $e^+e^- \rightarrow D_s^+ \overline{D}{}^{(*)0} K^-$ and study of the $P$-wave $D_s$ mesons

Studies of $e^+e^- \to D_s^+ \overline{D}{}^{(*)0}K^-$ and the $P$-wave charmed-strange mesons are performed based on an $e^+e^-$ collision data sample corresponding to an integrated luminosity of 567 pb$^{-1}$ collected with the BESIII detector at $\sqrt{s}= 4.600$ GeV. The processes of $e^+e^-\to D_s^+ \overline{D}{*}^{0} K^-$ and $D_s^+ \overline{D}{}^{0} K^-$ are observed for the first time and are found to be dominated by the modes $D_s^+ D_{s1}(2536)^-$ and $D_s^+ D^*_{s2}(2573)^-$, respectively. The Born cross sections are measured to be $σ^{B}(e^+e^-\to D_s^+ \overline{D}{*}^{0} K^-) = (10.1\pm2.3\pm0.8) pb$ and $σ^{B}(e^+e^-\to D_s^+ \overline{D}{}^{0} K^-) = (19.4\pm2.3\pm1.6) pb$, and the products of Born cross section and the decay branching fraction are measured to be $σ^{B}(e^+e^-\to D_s^+D_{s1}(2536)^- + c.c.)\cdot\mathcal{B}(D_{s1}(2536)^- \to \overline{D}{*}^{0} K^-) = (7.5 \pm 1.8 \pm 0.7) pb$ and $σ^{B}(e^+e^-\to D_s^+ D^*_{s2}(2573)^- + c.c.)\cdot\mathcal{B}(D^*_{s2}(2573)^- \to \overline{D}{}^{0} K^-) = (19.7 \pm 2.9 \pm 2.0) pb$. For the $D_{s1}(2536)^-$ and $D^*_{s2}(2573)^-$ mesons, the masses and widths are measured to be $M(D_{s1}(2536)^-) = (2537.7 \pm 0.5 \pm 3.1)~MeV/c^2,$ $ Γ(D_{s1}(2536)^-)) = (1.7\pm 1.2 \pm 0.6)~\rm MeV,$ and $M(D^*_{s2}(2573)^-) = (2570.7\pm 2.0 \pm 1.7)~MeV/c^2,$ $Γ(D^*_{s2}(2573)^-) = (17.2 \pm 3.6 \pm 1.1)~\rm MeV.$ The spin-parity of the $D^*_{s2}(2573)^-$ meson is determined to be $J^P=2^{+}$. In addition, the process $e^+e^-\to D_s^+ \overline{D}{}^{(*)0} K^-$ are searched for using the data samples taken at four (two) center-of-mass energies between 4.416 (4.527) and 4.575 GeV, and upper limits at the $90\%$ confidence level on the cross sections are determined.

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arXiv2018

Observation of $ψ(3686) \to p \bar{p} η^{\prime}$ and improved measurement of $J/ψ\to p \bar{p} η^{\prime}$

We observe the process $ψ(3686) \to p \bar{p} η^{\prime}$ for the first time, with a statistical significance higher than 10$σ$, and measure the branching fraction of $J/ψ\to p \bar{p} η^{\prime}$ with an improved accuracy compared to earlier studies. The measurements are based on $4.48 \times 10^8$ $ψ(3686)$ and $1.31 \times 10^{9}$ $J/ψ$ events collected by the BESIII detector operating at the BEPCII. The branching fractions are determined to be $B(ψ(3686) \to p \bar{p} η^{\prime}) = (1.10\pm0.10\pm0.08)\times10^{-5}$ and $B(J/ψ\to p \bar{p} η^{\prime})=(1.26\pm0.02\pm 0.07)\times10^{-4}$, where the first uncertainties are statistical and the second ones systematic. Additionally, the $η-η^{\prime}$ mixing angle is determined to be $-24^{\circ} \pm 11^{\circ}$ based on $ψ(3686) \to p \bar{p} η^{\prime}$, and $-24^{\circ} \pm 9^{\circ}$ based on $J/ψ\to p \bar{p} η^{\prime}$, respectively.

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arXiv2018

Measurements of the absolute branching fractions and $CP$ asymmetries for $D^+\rightarrow K_{S,L}^0 K^+(π^0)$

Using $e^+e^-$ collision 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 determine the absolute branching fractions $\mathcal{B}(D^+\rightarrow K_S^0 K^+)$ = $(3.02 \pm 0.09 \pm 0.08)\times10^{-3}$, $\mathcal{B}(D^+\rightarrow K_S^0 K^+ π^0)$ = $(5.07 \pm 0.19 \pm 0.23)\times10^{-3}$, $\mathcal{B}(D^+\rightarrow K_L^0 K^+)$ = $(3.21 \pm 0.11 \pm 0.11)\times10^{-3}$, and $\mathcal{B}(D^+\rightarrow K_L^0 K^+ π^0)$ = $(5.24 \pm 0.22 \pm 0.22)\times10^{-3}$, where the first and second uncertainties are statistical and systematic, respectively. The branching fraction \wbrksk is consistent with the world average value and the other three branching fractions are measured for the first time. We also measure the $CP$ asymmetries for the four decays and do not find a significant deviation from zero.

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arXiv2018

Azimuthal asymmetries of charged hadrons produced in high-energy muon scattering off longitudinally polarised deuterons

Single hadron azimuthal asymmetries of positive and negative hadrons produced in muon semi-inclusive deep inelastic scattering off longitudinally polarised deuterons are determined using the 2006 COMPASS data and also combined all deuteron COMPASS data. For each hadron charge, the dependence of the azimuthal asymmetry on the hadron azimuthal angle $ϕ$ is obtained by means of a five-parameter fitting function that besides a $ϕ$-independent term includes four modulations predicted by theory: $\sinϕ$, $\sin 2 ϕ$, $\sin 3ϕ$ and $\cosϕ$. The amplitudes of the five terms have been extracted, first, for the hadrons in the whole available kinematic region. In further fits, performed for hadrons from a restricted kinematic region, the $ϕ$-dependence is determined as a function of one of three variables (Bjorken-$x$, fractional energy of virtual photon taken by the outgoing hadron and hadron transverse momentum), while disregarding the others. Except the $ϕ$-independent term, all the modulation amplitudes are very small, and no clear kinematic dependence could be observed within experimental uncertainties.

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arXiv2018

A model to explain angular distributions of $J/ψ$ and $ψ(2S)$ decays into $Λ\overlineΛ$ and $Σ^0\overlineΣ^0$

BESIII data show a particular angular distribution for the decay of the $J/ψ$ and $ψ(2S)$ mesons into the hyperons $Λ\overlineΛ$ and $Σ^0\overlineΣ^0$. More in details the angular distribution of the decay $ψ(2S) \to Σ^0\overlineΣ^0$ exhibits an opposite trend with respect to that of the other three channels: $J/ψ\to Λ\overlineΛ$, $J/ψ\to Σ^0\overlineΣ^0$ and $ψ(2S) \to Λ\overlineΛ$. We define a model to explain the origin of this phenomenon.

hep-ph↗

arXiv2018

Measurement of $e^{+} e^{-} \rightarrow K^{+} K^{-}$ cross section at $\sqrt{s} = 2.00 - 3.08$ GeV

The cross section of the process $e^{+} e^{-} \rightarrow K^{+} K^{-}$ is measured at a number of center-of-mass energies $\sqrt{s}$ from 2.00 to 3.08 GeV with the BESIII detector at the Beijing Electron Positron Collider (BEPCII). The results provide the best precision achieved so far. A resonant structure around 2.2 GeV is observed in the cross section line shape. A Breit-Wigner fit yields a mass of $M=2239.2 \pm 7.1 \pm 11.3$~and a width of $Γ=139.8\pm12.3\pm20.6$ MeV, where the first uncertainties are statistical and the second ones are systematic. In addition, the time-like electromagnetic form factor of the kaon is determined at the individual center-of-mass energy points.

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arXiv2018

Dalitz Plot Analysis of the Decay $ω\rightarrow π^{+}π^{-}π^{0}$

Using a low-background sample of $2.6\times 10^5$ $J/ψ\rightarrowωη(ω\rightarrowπ^{+}π^{-}π^{0},η\rightarrowγγ)$ events, about 5 times larger statistics than previous experiments, we present a Dalitz plot analysis of the decay $ω\rightarrowπ^{+}π^{-}π^{0}$. It is found that the Dalitz plot distribution differs from the pure $P$-wave phase space with a statistical significance of $18.9σ$. The parameters from the fit to data are in reasonable agreement with those without the cross-channel effect within the dispersive framework, which indicates that the cross-channel effect in $ω\rightarrowπ^+π^-π^0$ is not significant.

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arXiv2018

Observation of the $W$-Annihilation Decay $D^{+}_{s} \rightarrow ωπ^{+}$ and Evidence for $D^{+}_{s} \rightarrow ωK^{+}$

We report on the observation of the $W$-annihilation decay $D^{+}_{s} \rightarrow ωπ^{+}$ and the evidence for $D_{s}^{+} \rightarrow ωK^{+}$ with a data sample corresponding to an integrated luminosity of 3.19 fb$^{-1}$ collected with the BESIII detector at the center-of-mass energy $\sqrt{s} = 4.178$ GeV. We obtain the branching fractions $\mathcal{B}(D^{+}_{s} \rightarrow ωπ^{+}) = (1.77\pm0.32_{\rm stat.}\pm0.11_{\rm sys.}) \times 10^{-3}$ and $\mathcal{B}(D^{+}_{s} \rightarrow ωK^{+}) = (0.87\pm0.24_{\rm stat.}\pm0.07_{\rm sys.}) \times 10^{-3}$, respectively.

hep-ex↗

arXiv2018

Measurement of the Branching Fraction For the Semi-Leptonic Decays $D^{0(+)}\to π^{-(0)}μ^+ν_μ$ and Test of Lepton Flavor Universality

Using a data sample corresponding to an integrated luminosity of $2.93\,\rm fb^{-1}$ taken at a center-of-mass energy of 3.773\,GeV with the BESIII detector operated at the BEPCII collider, we perform an analysis of the semi-leptonic decays $D^{0(+)}\to π^{-(0)}μ^+ν_μ$. The branching fractions of $D^0\to π^-μ^+ν_μ$ and $D^+\to π^0μ^+ν_μ$ are measured to be $(0.272 \pm 0.008_{\rm stat.} \pm 0.006_{\rm syst.})\%$ and $(0.350 \pm 0.011_{\rm stat.} \pm 0.010_{\rm syst.})\%$, respectively, where the former is of much improved precision compared to previous results and the latter is determined for the first time. Using these results along with previous BESIII measurements of $D^{0(+)}\to π^{-(0)}e^+ν_e$, we calculate the branching fraction ratios to be ${\mathcal R}^0\equiv {\mathcal B}_{D^{0}\to π^{-}μ^+ν_μ}/{\mathcal B}_{D^{0}\to π^{-}e^+ν_e}=0.922\pm 0.030_{\rm stat.}\pm0.022_{\rm syst.}$ and ${\mathcal R}^+\equiv {\mathcal B}_{D^{+}\to π^{0}μ^+ν_μ}/{\mathcal B}_{D^{+}\to π^{0}e^+ν_e}=0.964\pm 0.037_{\rm stat.}\pm0.026_{\rm syst.}$, which are compatible with the theoretical expectation of lepton flavor universality within $1.7σ$ and $0.5σ$, respectively. We also examine the branching fraction ratios in different four-momentum transfer square regions, and find no significant deviations from the standard model predictions.

hep-ex↗

arXiv2018

Light isovector resonances in $π^- p \to π^-π^-π^+ p$ at 190 GeV/${\it c}$

We have performed the most comprehensive resonance-model fit of $π^-π^-π^+$ states using the results of our previously published partial-wave analysis (PWA) of a large data set of diffractive-dissociation events from the reaction $π^- + p \to π^-π^-π^+ + p_\text{recoil}$ with a 190 GeV/$c$ pion beam. The PWA results, which were obtained in 100 bins of three-pion mass, $0.5 < m_{3π} < 2.5$ GeV/$c^2$, and simultaneously in 11 bins of the reduced four-momentum transfer squared, $0.1 < t' < 1.0$ $($GeV$/c)^2$, are subjected to a resonance-model fit using Breit-Wigner amplitudes to simultaneously describe a subset of 14 selected waves using 11 isovector light-meson states with $J^{PC} = 0^{-+}$, $1^{++}$, $2^{++}$, $2^{-+}$, $4^{++}$, and spin-exotic $1^{-+}$ quantum numbers. The model contains the well-known resonances $π(1800)$, $a_1(1260)$, $a_2(1320)$, $π_2(1670)$, $π_2(1880)$, and $a_4(2040)$. In addition, it includes the disputed $π_1(1600)$, the excited states $a_1(1640)$, $a_2(1700)$, and $π_2(2005)$, as well as the resonancelike $a_1(1420)$. We measure the resonance parameters mass and width of these objects by combining the information from the PWA results obtained in the 11 $t'$ bins. We extract the relative branching fractions of the $ρ(770) π$ and $f_2(1270) π$ decays of $a_2(1320)$ and $a_4(2040)$, where the former one is measured for the first time. In a novel approach, we extract the $t'$ dependence of the intensity of the resonances and of their phases. The $t'$ dependence of the intensities of most resonances differs distinctly from the $t'$ dependence of the nonresonant components. For the first time, we determine the $t'$ dependence of the phases of the production amplitudes and confirm that the production mechanism of the Pomeron exchange is common to all resonances.

hep-ex↗

arXiv2018

Observation of $h_1(1380)$ in the $J/ψ\to η^{\prime} K\bar K π$ Decay

Using $1.31 \times 10^9$ $J/ψ$ events collected by the BESIII detector at the BEPCII $e^+e^-$ collider, we report the first observation of the $h_1(1380)$ in $J/ψ\to η^{\prime} h_1(1380)$ with a significance of more than ten standard deviations. The mass and width of the possible axial-vector strangeonium candidate $h_1(1380)$ are measured to be $M = (1423.2 \pm 2.1 \pm 7.3)\mevcc$ and $Γ= (90.3 \pm 9.8 \pm 17.5)\mev$. The product branching fractions, assuming no interference, are determined to be $\mathcal{B}(J/ψ\to η^{\prime}h_1(1380)) \times \mathcal{B}(h_1(1380) \to K^{*}(892)^{+} K^{-} +c.c.) = (1.51 \pm 0.09 \pm 0.21) \times 10^{-4}$ in $η^{\prime}K^+K^-π^0$ mode and $\mathcal{B}(J/ψ\to η^{\prime}h_1(1380)) \times \mathcal{B}(h_1(1380) \to K^{*}(892)\bar K +c.c.) = (2.16 \pm 0.12 \pm 0.29) \times 10^{-4}$ in $η^{\prime}K_S^0K^{\pm}π^{\mp}$ mode. The first uncertainties are statistical and the second are systematic. Isospin symmetry violation is observed in the decays $h_1(1380) \to K^{*}(892)^{+} K^{-} +c.c.$ and $h_1(1380) \to K^{*}(892)^{0}\bar K^{0} +c.c.$. Based on the measured $h_1(1380)$ mass, the mixing angle between the states $h_1(1170)$ and $h_1(1380)$ is determined to be $(35.9\pm2.6)^{\circ}$, consistent with theoretical expectations.

hep-ex↗

arXiv2018

Measurements of $e^+e^- \to K_{S}^{0}K^{\pm}π^{\mp}π^0$ and $K_{S}^{0}K^{\pm}π^{\mp}η$ at center-of-mass energies from $3.90$ to $4.60~\mathrm{GeV}$

Using $5.2 \ \mathrm{fb}^{-1}$ $e^+ e^-$ annihilation data samples collected with the BESIII detector, we measure the cross sections of $e^+e^- \to K_S^0 K^\pm π^\mp π^0$ and $K_{S}^{0}K^{\pm}π^{\mp}η$ at center-of-mass energies from $3.90$ to $4.60$ GeV. In addition, we search for the charmonium-like resonance $Y(4260)$ decays into $K_{S}^{0}K^{\pm}π^{\mp}π^0$ and $K_{S}^{0}K^{\pm}π^{\mp}η$, and $Z_c^{0,\pm}(3900)$ decays into $K_{S}^{0}K^{\pm}π^{\mp,0}$ and $K_{S}^{0}K^{\pm}η$. Corresponding upper limits are provided since no clear signal is observed.

hep-ex↗

arXiv2018

K$^{-}$ over K$^{+}$ multiplicity ratio for kaons produced in DIS with a large fraction of the virtual-photon energy

The K$^{-}$ over K$^{+}$ multiplicity ratio is measured in deep-inelastic scattering, for the first time for kaons carrying a large fraction $z$ of the virtual-photon energy. The data were obtained by the COMPASS collaboration using a 160 GeV muon beam and an isoscalar $^6$LiD target. The regime of deep-inelastic scattering is ensured by requiring $Q^2>1$ (GeV/$c)^2$ for the photon virtuality and $W>5$ GeV/$c^2$ for the invariant mass of the produced hadronic system. Kaons are identified in the momentum range from 12 GeV/$c$ to 40 GeV/$c$, thereby restricting the range in Bjorken-$x$ to $0.01 0.75$. For very large values of $z$, $i.e.$ $z>0.8$, we observe the kaon multiplicity ratio to fall below the lower limits expected from calculations based on leading and next-to-leading order perturbative quantum chromodynamics. Also, the kaon multiplicity ratio shows a strong dependence on the missing mass of the single-kaon production process. This suggests that within the perturbative quantum chromodynamics formalism an additional correction may be required, which takes into account the phase space available for hadronisation.

hep-ex↗

arXiv2018

Measurement of $P_T$-weighted Sivers asymmetries in leptoproduction of hadrons

The transverse spin asymmetries measured in semi-inclusive leptoproduction of hadrons, when weighted with the hadron transverse momentum $P_T$, allow for the extraction of important transverse-momentum-dependent distribution functions. In particular, the weighted Sivers asymmetries provide direct information on the Sivers function, which is a leading-twist distribution that arises from a correlation between the transverse momentum of an unpolarised quark in a transversely polarised nucleon and the spin of the nucleon. Using the high-statistics data collected by the COMPASS Collaboration in 2010 with a transversely polarised proton target, we have evaluated two types of $P_T$-weighted Sivers asymmetries, which are both proportional to the product of the firsttransverse moment of the Sivers function and of the fragmentation function. The results are compared to the standard unweighted Sivers asymmetries and used to extract the first transverse moments of the Sivers distributions for $u$ and $d$ quarks.

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