arXiv subjects

A. Chen

Publications and source records attributed to A. Chen.

At least 199 records · Page 11Linked to original sources

arXiv2019

H.E.S.S. and Fermi-LAT observations of PSR B1259-63/LS 2883 during its 2014 and 2017 periastron passages

PSR B1259-63/LS 2883 is a gamma-ray binary system consisting of a pulsar in an eccentric orbit around a bright Oe stellar-type companion star that features a dense circumstellar disc. The high- and very-high-energy (HE, VHE) gamma-ray emission from PSR B1259-63/LS 2883 around the times of its periastron passage are characterised, in particular, at the time of the HE gamma-ray flares reported to have occurred in 2011, 2014, and 2017. Spectra and light curves were derived from observations conducted with the H.E.S.S.-II array in 2014 and 2017. A local double-peak profile with asymmetric peaks in the VHE light curve is measured, with a flux minimum at the time of periastron $t_p$ and two peaks coinciding with the times at which the neutron star crosses the companion's circumstellar disc ($\sim t_p \pm 16$ d). A high VHE gamma-ray flux is also observed at the times of the HE gamma-ray flares ($\sim t_p + 30$ d) and at phases before the first disc crossing ($\sim t_p - 35$ d). PSR B1259-63/LS 2883 displays periodic flux variability at VHE gamma-rays without clear signatures of super-orbital modulation in the time span covered by H.E.S.S. observations. In contrast, the photon index of the measured power-law spectra remains unchanged within uncertainties for about 200 d around periastron. Lower limits on exponential cut-off energies up to $\sim 40$ TeV are placed. At HE gamma-rays, PSR B1259-63/LS 2883 has now been detected also before and after periastron, close to the disc crossing times. Repetitive flares with distinct variability patterns are detected in this energy range. Such outbursts are not observed at VHEs, although a relatively high emission level is measured. The spectra obtained in both energy regimes displays a similar slope, although a common physical origin either in terms of a related particle population, emission mechanism, or emitter location is ruled out.

astro-ph.HE↗

arXiv2019

Experience with Long-pulse Operation of the PIP2IT Warm Front End

The warm front end of the PIP2IT accelerator, assem-bled and commissioned at Fermilab, consists of a 15 mA DC, 30 keV H- ion source, a 2 m long Low Energy Beam Transport (LEBT) line, and a 2.1 MeV, 162.5 MHz CW RFQ, followed by a 10 m long Medium Energy Beam Transport (MEBT) line. A part of the commissioning efforts involves operation with the average beam power emulating the operation of the proposed PIP-II accelera-tor, which will have a duty factor of 1.1% or above. The maximum achieved power is 5 kW (2.1 MeV x 5 mA x 25 ms x 20 Hz). This paper describes the difficulties encoun-tered and some of the solutions that were implemented.

physics.acc-ph↗

arXiv2019

Test Results of PIP2IT MEBT Vacuum Protection System

The central part of PIP-II program of upgrades pro-posed for the Fermilab injection complex is an 800 MeV, 2 mA, CW-compatible SRF linac. Acceleration in super-conducting cavities begins from a low energy of 2.1 MeV, so that the first cryomodule, Half Wave Resonator (HWR) borders the warm Medium Beam Transport (MEBT) line. To minimize the amount of gas that may enter the SRF linac in a case if a vacuum failure occurs in the warm front end, a vacuum protection system is envisioned to be used in the PIP-II MEBT. It features a fast closing valve with two sensors and a differential pumping insert. The system prototype was installed in the PIP-II Injector Test (PIP2IT) accelerator and successfully tested in several modes modelling the vacuum failures. The report presents the design of the vacuum protection system and results of its tests.

physics.acc-ph↗

arXiv2019

A very-high-energy component deep in the Gamma-ray Burst afterglow

Gamma-ray bursts (GRBs) are brief flashes of gamma rays, considered to be the most energetic explosive phenomena in the Universe. The emission from GRBs comprises a short (typically tens of seconds) and bright prompt emission, followed by a much longer afterglow phase. During the afterglow phase, the shocked outflow -- produced by the interaction between the ejected matter and the circumburst medium -- slows down, and a gradual decrease in brightness is observed. GRBs typically emit most of their energy via gamma-rays with energies in the kiloelectronvolt-to-megaelectronvolt range, but a few photons with energies of tens of gigaelectronvolts have been detected by space-based instruments. However, the origins of such high-energy (above one gigaelectronvolt) photons and the presence of very-high-energy (more than 100 gigaelectronvolts) emission have remained elussive. Here we report observations of very-high-energy emission in the bright GRB 180720B deep in the GRB afterglow -ten hours after the end of the prompt emission phase, when the X-ray flux had already decayed by four orders of magnitude. Two possible explanations exist for the observed radiation: inverse Compton emission and synchrotron emission of ultrarelativistic electrons. Our observations show that the energy fluxes in the X-ray and gamma-ray range and their photon indices remain comparable to each other throughout the afterglow. This discovery places distinct constraints on the GRB environment for both emission mechanisms, with the inverse Compton explanation alleviating the particle energy requirements for the emission observed at late times. The late timing of this detection has consequences for the future observations of GRBs at the highest energies.

astro-ph.HE↗

arXiv2019

H.E.S.S. detection of very-high-energy gamma-ray emission from the quasar PKS 0736+017

Flat-spectrum radio-quasars (FSRQs) are rarely detected at very-high-energies (VHE; E>100 GeV) due to their low-frequency-peaked SEDs. At present, only 6 FSRQs are known to emit VHE photons, representing only 7% of the VHE extragalactic catalog. Following the detection of MeV-GeV gamma-ray flaring activity from the FSRQ PKS 0736+017 (z=0.189) with Fermi, the H.E.S.S. array of Cherenkov telescopes triggered ToO observations on February 18, 2015, with the goal of studying the gamma-ray emission in the VHE band. H.E.S.S. ToO observations were carried out during the nights of February 18, 19, 21, and 24, 2015. Together with Fermi-LAT, the multi-wavelength coverage of the flare includes Swift observations in soft-X-rays and optical/UV, and optical monitoring (photometry and spectro-polarimetry) by the Steward Observatory, the ATOM, the KAIT and the ASAS-SN telescope. VHE emission from PKS 0736+017 was detected with H.E.S.S. during the night of February 19, 2015, only. Fermi data indicate the presence of a gamma-ray flare, peaking at the time of the H.E.S.S. detection, with a flux doubling time-scale of around six hours. The gamma-ray flare was accompanied by at least a 1 mag brightening of the non-thermal optical continuum. No simultaneous observations at longer wavelengths are available for the night of the H.E.S.S. detection. The gamma-ray observations with H.E.S.S. and Fermi are used to put constraints on the location of the gamma-ray emitting region during the flare: it is constrained to be just outside the radius of the broad-line-region with a bulk Lorentz factor $\simeq 20$, or at the level of the radius of the dusty torus with Gamma > 60. PKS 0736+017 is the seventh FSRQ known to emit VHE photons and, at z=0.189, is the nearest so far. The location of the gamma-ray emitting region during the flare can be tightly constrained thanks to opacity, variability, and collimation arguments.

astro-ph.HE↗

arXiv2019

Search for $B^+ \to μ^+\, ν_μ$ and $B^+ \to μ^+\, N$ with inclusive tagging

We report the result for a search for the leptonic decay of $B^+ \to μ^+ \, ν_μ$ using the full Belle data set of 711 fb${}^{-1}$ of integrated luminosity at the $Υ(4S)$ resonance. In the Standard Model leptonic $B$-meson decays are helicity and CKM suppressed. To maximize sensitivity an inclusive tagging approach is used to reconstruct the second $B$ meson produced in the collision. The directional information from this second $B$ meson is used to boost the observed $μ$ into the signal $B$ meson rest-frame, in which the $μ$ has a monochromatic momentum spectrum. Though its momentum is smeared by the experimental resolution, this technique improves the analysis sensitivity considerably. Analyzing the $μ$ momentum spectrum in this frame we find $\mathcal{B}(B^+ \to μ^+ \, ν_μ) = \left( 5.3 \pm 2.0 \pm 0.9 \right) \times 10^{-7}$ with a one-sided significance of 2.8 standard deviations over the background-only hypothesis. This translates to a frequentist upper limit of $\mathcal{B}(B^+ \to μ^+ \, ν_μ) < 8.6 \times 10^{-7}$ at 90% CL. The experimental spectrum is then used to search for a massive sterile neutrino, $B^+ \to μ^+ \, N$, but no evidence is observed for a sterile neutrino with a mass in a range of 0 - 1.5 GeV. The determined $B^+ \to μ^+ \, ν_μ$ branching fraction limit is further used to constrain the mass and coupling space of the type II and type III two-Higgs-doublet models.

hep-ex↗

arXiv2019

Dark Energy Survey Year 1 Results: Constraints on Extended Cosmological Models from Galaxy Clustering and Weak Lensing

We present constraints on extensions of the minimal cosmological models dominated by dark matter and dark energy, $Λ$CDM and $w$CDM, by using a combined analysis of galaxy clustering and weak gravitational lensing from the first-year data of the Dark Energy Survey (DES Y1) in combination with external data. We consider four extensions of the minimal dark energy-dominated scenarios: 1) nonzero curvature $Ω_k$, 2) number of relativistic species $N_{\rm eff}$ different from the standard value of 3.046, 3) time-varying equation-of-state of dark energy described by the parameters $w_0$ and $w_a$ (alternatively quoted by the values at the pivot redshift, $w_p$, and $w_a$), and 4) modified gravity described by the parameters $μ_0$ and $Σ_0$ that modify the metric potentials. We also consider external information from Planck CMB measurements; BAO measurements from SDSS, 6dF, and BOSS; RSD measurements from BOSS; and SNIa information from the Pantheon compilation. Constraints on curvature and the number of relativistic species are dominated by the external data; when these are combined with DES Y1, we find $Ω_k=0.0020^{+0.0037}_{-0.0032}$ at the 68% confidence level, and $N_{\rm eff}<3.28\, (3.55)$ at 68% (95%) confidence. For the time-varying equation-of-state, we find the pivot value $(w_p, w_a)=(-0.91^{+0.19}_{-0.23}, -0.57^{+0.93}_{-1.11})$ at pivot redshift $z_p=0.27$ from DES alone, and $(w_p, w_a)=(-1.01^{+0.04}_{-0.04}, -0.28^{+0.37}_{-0.48})$ at $z_p=0.20$ from DES Y1 combined with external data; in either case we find no evidence for the temporal variation of the equation of state. For modified gravity, we find the present-day value of the relevant parameters to be $Σ_0= 0.43^{+0.28}_{-0.29}$ from DES Y1 alone, and $(Σ_0, μ_0)=(0.06^{+0.08}_{-0.07}, -0.11^{+0.42}_{-0.46})$ from DES Y1 combined with external data, consistent with predictions from GR.

astro-ph.CO↗

arXiv2019

Observation of a vector charmoniumlike state in $e^+e^- \to D^+_sD_{s1}(2536)^-+c.c.$

Using a data sample of 921.9 fb$^{-1}$ collected with the Belle detector, we study the process of $e^+e^-\to D^+_sD_{s1}(2536)^-+c.c.$ via initial-state radiation. We report the first observation of a vector charmoniumlike state decaying to $D^+_sD_{s1}(2536)^-+c.c.$ with a significance of 5.9$σ$, including the systematic uncertainties. The measured mass and width are $(4625.9^{+6.2}_{-6.0}({\rm stat.})\pm0.4({\rm syst.}))~{\rm MeV}/c^{2}$ and $(49.8^{+13.9}_{-11.5}({\rm stat.})\pm4.0({\rm syst.}))~{\rm MeV}$, respectively. The product of the $e^+e^-\to D^+_sD_{s1}(2536)^-+c.c.$ cross section and the branching fraction of $D_{s1}(2536)^-\to{\bar D}^{*0}K^-$ is measured from the $D_s \bar{D}_{s1}(2536)$ threshold to 5.59~GeV.

hep-ex↗

arXiv2019

Observation of the radiative decays of $Υ(1S)$ to $χ_{c1}$

We report the first observation of the radiative decay of the $Υ(1S)$ into a charmonium state. The statistical significance of the observed signal of $Υ(1S) \to γχ_{c1}$ is 6.3 standard deviations including systematics. The branching fraction is calculated to be Br($Υ(1S) \to γχ_{c1}$) = (4.7^{+2.4}_{-1.8} (stat) ^{+0.4}_{-0.5} (sys)) * 10^{-5}. We also searched for $Υ(1S)$ radiative decays into $χ_{c0,2}$ and $η_c(1S,2S)$ and set upper limits on their branching fractions. These results are obtained from a 24.9 fb^{-1} data sample collected with the Belle detector at the KEKB asymmetric-energy $e^+e^-$ collider at a center-of-mass energy equal to the $Υ(2S)$ mass using $Υ(1S)$ tagging by the $Υ(2S) \to Υ(1S) π^+π^-$ transitions.

hep-ex↗

arXiv2019

Measurement of $\mathcal{R}(D)$ and $\mathcal{R}(D^*)$ with a semileptonic tagging method

The experimental results on the ratios of branching fractions $\mathcal{R}(D) = {\cal B}(\bar{B} \to D τ^- \barν_τ)/{\cal B}(\bar{B} \to D \ell^- \barν_{\ell})$ and $\mathcal{R}(D^*) = {\cal B}(\bar{B} \to D^* τ^- \barν_τ)/{\cal B}(\bar{B} \to D^* \ell^- \barν_{\ell})$, where $\ell$ denotes an electron or a muon, show a long-standing discrepancy with the Standard Model predictions, and might hint to a violation of lepton flavor universality. We report a new simultaneous measurement of $\mathcal{R}(D)$ and $\mathcal{R}(D^*)$, based on a data sample containing $772 \times 10^6$ $B\bar{B}$ events recorded at the $Υ(4S)$ resonance with the Belle detector at the KEKB $e^+ e^-$ collider. In this analysis the tag-side $B$ meson is reconstructed in a semileptonic decay mode and the signal-side $τ$ is reconstructed in a purely leptonic decay. The measured values are $\mathcal{R}(D)= 0.307 \pm 0.037 \pm 0.016$ and $\mathcal{R}(D^*) = 0.283 \pm 0.018 \pm 0.014$, where the first uncertainties are statistical and the second are systematic. These results are in agreement with the Standard Model predictions within $0.2$, $1.1$ and $0.8$ standard deviations for $\mathcal{R}(D)$, $\mathcal{R}(D^*)$ and their combination, respectively. This work constitutes the most precise measurements of $\mathcal{R}(D)$ and $\mathcal{R}(D^*)$ performed to date as well as the first result for $\mathcal{R}(D)$ based on a semileptonic tagging method.

hep-ex↗

arXiv2019

Observation of a new structure near 10.75 GeV in the energy dependence of the $e^+e^-\toΥ(nS)π^+π^-$ ($n=1,2,3$) cross sections

We report a new measurement of the $e^+e^-\toΥ(nS)π^+π^-$ ($n=1,2,3$) cross sections at energies from 10.52 to 11.02 GeV using data collected with the Belle detector at the KEKB asymmetric-energy $e^+e^-$ collider. We observe a new structure in the energy dependence of the cross sections; if described by a Breit-Wigner function its mass and width are found to be $M=(10752.7\pm5.9\,^{+0.7}_{-1.1})\,$MeV/$c^2$ and $Γ=(35.5^{+17.6}_{-11.3}\,^{+3.9}_{-3.3})\,$MeV, where the first error is statistical and the second is systematic. The global significance of the new structure including systematic uncertainty is 5.2 standard deviations. We also find evidence for the $e^+e^-\toΥ(1S)π^+π^-$ process at the energy 10.52 GeV, which is below the $B\bar{B}$ threshold.

hep-ex↗

arXiv2019

First measurement of the CKM angle $ϕ_3$ with $B^{\pm}\to D(K_{\rm S}^0π^+π^-π^0)K^{\pm}$ decays

We present the first model-independent measurement of the CKM unitarity triangle angle $ϕ_3$ using $B^{\pm}\to D(K_{\rm S}^0π^+π^-π^0)K^{\pm}$ decays, where $D$ indicates either a $D^{0}$ or $\overline{D}^{0}$ meson. Measurements of the strong-phase difference of the $D \to K_{\rm S}^0π^+π^-π^0$ amplitude obtained from CLEO-c data are used as input. This analysis is based on the full Belle data set of $772\times 10^{6}$ $B\overline{B}$ events collected at the $Υ(4S)$ resonance. We obtain $ϕ_3 = (5.7~^{+10.2}_{-8.8} \pm 3.5 \pm 5.7)^{\circ}$ and the suppressed amplitude ratio $r_{B} = 0.323 \pm 0.147 \pm 0.023 \pm 0.051$. Here the first uncertainty is statistical, the second is the experimental systematic, and the third is due to the precision of the strong-phase parameters measured from CLEO-c data. The 95% confidence interval on $ϕ_3$ is $(-29.7,~109.5)^{\circ}$, which is consistent with the current world average.

hep-ex↗

arXiv2019

First inverse kinematics study of the $^{22}$Ne$(p,γ)^{23}$Na reaction and its role in AGB star and classical nova nucleosynthesis

The abundances of sodium and oxygen are observed to be anti-correlated in all well-studied globular clusters. Asymptotic giant branch (AGB) stars undergoing hot bottom burning (HBB) are thought to be prime candidates for producing sodium-rich oxygen-poor material and expelling it into the cluster ISM. The 22Ne(p,gamma)23Na reaction has been shown to strongly influence the amount of 23Na produced during HBB. This reaction is also important for classical novae nucleosynthesis, with sensitivity studies showing that the abundances of several isotopes in the Ne-Al region are significantly altered when varying the reaction rate between available compilations. Here we present the first inverse kinematics measurements of key resonances strengths as well as the direct capture S-factor. Together, this study represents the largest centre of mass energy range (149-1222 keV) over which this reaction has been measured in a single experiment. Our results for low-energy resonances at Ecm=149, 181 and 248 keV are in good agreement with recent forward kinematics results; we also find a direct capture S-factor consistent with the literature value of 62 keV.b. However, in the case of the important reference resonance at Ecm = 458 keV we find a strength value of wg=0.44 +/- 0.02 eV, which is significantly lower than recent results. Using our new recommended rate we explore the impact of these results on both AGB star and classical novae nucleosynthesis. In the case of AGB stars we see very little abundance changes with respect to the rate included in the STARLIB-2013. However, we observe changes of up to a factor of 2 in isotopes produced in both the carbon-oxygen (CO) and oxygen-neon (ONe) classical novae models considered here. The 22Ne(p,gamma)23Na reaction rate is now sufficiently well constrained to not significantly contribute toward abundance uncertainties from classical novae nucleosynthesis models.

nucl-ex↗

arXiv2019

Observation of $ τ^- \rightarrow π^- ν_τ e^+ e^-$ and search for $τ^- \rightarrow π^- ν_τ μ^+ μ^-$

We present the first measurements of branching fractions of rare tau-lepton decays, $τ^- \rightarrow π^- ν_τ \ell^+ \ell^-$ ($\ell = e$ or $μ$), using a data sample corresponding to 562 fb$^{-1}$ collected at a center-of-mass energy of 10.58 GeV with the Belle detector at the KEKB asymmetric-energy $e^+ e^-$ collider. The $τ^- \rightarrow π^- ν_τe^+ e^-$ decay is observed for the first time with 7.0$σ$ significance. The partial branching fraction determined by the structure-dependent mechanisms mediated by either a vector or an axial-vector current for the mass region $M_{πe e}>1.05$ GeV/$c^2$ is measured to be $\mathcal{B}(τ^-\rightarrow π^- ν_τe^+ e^-)[M_{π^- e^+ e^-}>1.05~{\rm GeV}/c^2] = (5.90 \pm 0.53 \pm 0.85 \pm 0.11) \times 10^{-6}$, where the first uncertainty is statistical, the second is systematic, and the third is due to the model dependence. In the full phase space, due to the different detection efficiencies for the structure-dependent mechanisms mediated by axial-vector and vector currents, the branching fraction varies from $\mathcal{B}_{A}(τ^-\rightarrow π^- ν_τe^+ e^-) = (1.46 \pm 0.13 \pm 0.21) \times 10^{-5}$ to $\mathcal{B}_{V}(τ^-\rightarrow π^- ν_τe^+ e^-) = (3.01 \pm 0.27 \pm 0.43) \times 10^{-5}$, respectively. An upper limit is set on the branching fraction of the $τ^- \rightarrow π^- ν_τμ^+ μ^-$ decay, $\mathcal{B}(τ^-\rightarrow π^- ν_τμ^+ μ^-) < 1.14 \times 10^{-5}$, at the 90% confidence level.

hep-ex↗

arXiv2019

Resolving the Crab pulsar wind nebula at teraelectronvolt energies

The Crab nebula is one of the most studied cosmic particle accelerators, shining brightly across the entire electromagnetic spectrum up to very high-energy gamma rays. It is known from radio to gamma-ray observations that the nebula is powered by a pulsar, which converts most of its rotational energy losses into a highly relativistic outflow. This outflow powers a pulsar wind nebula (PWN), a region of up to 10~light-years across, filled with relativistic electrons and positrons. These particles emit synchrotron photons in the ambient magnetic field and produce very high-energy gamma rays by Compton up-scattering of ambient low-energy photons. While the synchrotron morphology of the nebula is well established, it was up to now not known in which region the very high-energy gamma rays are emitted. Here we report that the Crab nebula has an angular extension at gamma-ray energies of 52 arcseconds (assuming a Gaussian source width), significantly larger than at X-ray energies. This result closes a gap in the multi-wavelength coverage of the nebula, revealing the emission region of the highest energy gamma rays. These gamma rays are a new probe of a previously inaccessible electron and positron energy range. We find that simulations of the electromagnetic emission reproduce our new measurement, providing a non-trivial test of our understanding of particle acceleration in the Crab nebula.

astro-ph.HE↗

arXiv2019

Azimuthal asymmetries of back-to-back $π^\pm-(π^0,η,π^\pm)$ pairs in $e^+e^-$ annihilation

This work reports the first observation of azimuthal asymmetries around the thrust axis in $e^+e^-$ annihilation of pairs of back-to-back charged pions in one hemisphere, and $π^0$ and $η$ mesons in the opposite hemisphere. These results are complemented by a new analysis of pairs of back-to-back charged pions. The $π^0$ and $η$ asymmetries rise with the relative momentum $z$ of the detected hadrons as well as with the transverse momentum with respect to the thrust axis. These asymmetries are sensitive to the Collins fragmentation function $H_1^{\perp}$ and provide complementary information to previous measurements with charged pions and kaons in the final state. In particular, the $η$ final states will provide additional information on the flavor structure of $H_1^{\perp}$. This is the first measurement of the explicit transverse-momentum dependence of the Collins fragmentation function from Belle data. It uses a dataset of 980.4~fb$^{-1}$ collected by the Belle experiment at or near a center-of-mass energy of 10.58 GeV.

hep-ex↗

arXiv2019

Experimental determination of the isospin of $Λ_c(2765)^+/Σ_c(2765)^+$

We report an experimental determination of the isospin of $Λ_c(2765)^+/Σ_c(2765)^+$ using 980 fb$^{-1}$ data in the $e^+e^-$ annihilation around $\sqrt{s} = 10.6$ GeV collected by the Belle detector located at the KEKB collider. The isospin partners are searched for in the $Σ_c(2455)^{++/0} π^{0}$ channels, and no evidence was obtained. Thus the isospin is determined to be zero, and the particle is established to be a $Λ_c$.

hep-ex↗

arXiv2019

First measurements of absolute branching fractions of the $Ξ_c^+$ baryon at Belle

We present the first measurements of the absolute branching fractions of $Ξ_c^+$ decays into $Ξ^- π^+ π^+$ and $p K^- π^+$ final states. Our analysis is based on a data set of $(772\pm 11)\times 10^{6}$ $B\bar{B}$ pairs collected at the $Υ(4S)$ resonance with the Belle detector at the KEKB $e^+e^-$ collider. We measure the absolute branching fraction of $\bar{B}^{0} \to \barΛ_{c}^{-} Ξ_{c}^{+}$ with the $Ξ_c^+$ recoiling against $\barΛ_c^-$ in $\bar{B}^0$ decays resulting in ${\cal B}(\bar{B}^{0} \to \barΛ_{c}^{-} Ξ_{c}^{+}) = [1.16 \pm 0.42(\rm stat.) \pm 0.15(\rm syst.)] \times 10^{-3}$. We then measure the product branching fractions ${\cal B}(\bar{B}^{0} \to \barΛ_c^- Ξ_c^+){\cal B}(Ξ_c^+ \to Ξ^- π^+ π^+)$ and ${\cal B}(\bar{B}^{0} \to \barΛ_c^- Ξ_c^+){\cal B}(Ξ_c^+ \to p K^- π^+)$. Dividing these product branching fractions by $\bar{B}^{0} \to \barΛ_{c}^{-} Ξ_{c}^{+}$ yields: ${\cal B}(Ξ_c^+ \to Ξ^- π^+ π^+) = [2.86 \pm 1.21(\rm stat.) \pm 0.38(\rm syst.)]\%$ and ${\cal B}(Ξ_c^+ \to p K^- π^+)=[0.45 \pm 0.21(\rm stat.) \pm 0.07(\rm syst.)]\%$. Our result for ${\cal B}(Ξ_c^+ \to Ξ^- π^+ π^+)$ can be combined with $Ξ_c^+$ branching fractions measured relative to $Ξ_c^+ \to Ξ^- π^+ π^+$ to set the absolute scale for many $Ξ_c^+$ branching fractions.

hep-ex↗