On laser facilities for achieving inertial confinement fusion ignition,several beams are usually bundled together and injected into the target chamber through a common port.This specific configuration could lead to la...On laser facilities for achieving inertial confinement fusion ignition,several beams are usually bundled together and injected into the target chamber through a common port.This specific configuration could lead to laser-plasma interaction(LPI)processes that are quite different from those of a single laser beam,as well as to more options for suppressing LPI via combination of different laser smoothing techniques on the beams in a bundle.For studying LPI of a bundle of beams,a novel facility named Shenguang Octopus has been developed.Recently,the first LPI experiments have been performed by axially irradiating a gas-filled glass pipe or a gold hohlraum target with the bundled eight laser beams at an overlapped intensity of~1×1015W~cm2,producing~5-mm-long homogeneous plasmas with densities of~3×1020cm-3and temperatures of 1.2-1.5 keV.Efficient laser propagation without plasma filamentation and beam spraying has been observed via side-on X-ray images of glass pipe targets.Results from the gold hohlraum targets indicate that single-beam backward stimulated Brillouin scattering(SBS)and multibeam seeded side-SBS play major roles in the interaction,while other multibeam LPI processes expected before the experiments are not observed.Several beam smoothing techniques,such as mixed polarizations,smoothing by spectral dispersion,and multicolor mode,are demonstrated to be effective in suppressing LPI under current conditions.展开更多
Polysynthetic twinned(PST)TiAl single crystal specifically refers to a fully lamellar TiAl single crystal with parallel phase interfaces and twin interfaces grown by directional solidification.In this paper,PST single...Polysynthetic twinned(PST)TiAl single crystal specifically refers to a fully lamellar TiAl single crystal with parallel phase interfaces and twin interfaces grown by directional solidification.In this paper,PST single crystals with different phase ratios are obtained by annealing at specific temperatures and holding times.The results show that the diffusion rates of Ti and Al elements at various temperatures directly trigger and propel the surface recrystallization and variation in the internal phase ratio.When the temperature is lower than 1448 K,the diffusion rate of Ti is obviously higher than that of Al,which causes one denseα2recrystallized layer to form on the surface of TiAl single crystals.Meanwhile,as more Ti elements migrate to the surface,theα2phase ratio inside the TiAl single crystal thereby decreases.When the temperature exceeds 1448 K,the diffusion rate of Al gradually reverses to exceed that of Ti,which forms the surface sandwiched recrystallization dominated byγphase and simultaneously increasesα2phase ratio inside the TiAl single crystal.The variation in the two-phase ratio directly induces a significant change in the lamellae thickness,which exhibits different tensile behaviors of PST-TiAl single crystal.When theα2phase content is less than 20%,widerγlamellae make it easier for dislocations to be activated within its lamellae and continuously move across theγ/α2interfaces,thereby obtaining better tensile plasticity.As theα2phase content exceeds 30%,finerγlamellae inhibit the dislocation initiation,resulting in the fracture occurrence of TiAl single crystal before yielding.No matter how the phase ratio changes,the crack preferentially initiates withinα2lamellae.However,the crack propagation follows different paths based on variousγlamella thicknesses.The fracture mode of PST-TiAl single crystal also changes from shear fracture along slip bands within theγlamella to brittle fracture along the{1¯100}planes withinα2lamella.展开更多
Gradient structure is emerging as an effective strategy to fabricate metals with remarkable mechanical performance,but have not been verified in intermetallic compounds for high-temperature applications.Through experi...Gradient structure is emerging as an effective strategy to fabricate metals with remarkable mechanical performance,but have not been verified in intermetallic compounds for high-temperature applications.Through experiments and atomic simulations,we show that a typical intermetallic TiAl alloy with gra-dient structure has a significant strengthening effect both at room temperature and high temperatures.The room-temperature compressive strength of TiAl alloys with gradient grain obtained by additive man-ufacturing is 2.57 GPa,which is∼2.7 times as strong as that with equiaxed grain.The strengthening effect is attributed to more sessile dislocations in gradient structure caused by the intersections of mul-tiple slip systems in gradient grain.More importantly,the strengthening effect is still effective at high temperatures and the compressive strength is 1.28 GPa at 750°C.The simulation results show that this strengthening effect is due to the increased Hirth dislocation at high temperatures.This study expands the applications of TiAl alloys for load-bearing structures and provides a new strategy for improving the strength of intermetallic compounds at both room temperature and high temperatures.展开更多
The generation of ultrashort high-power light sources in the mid-infrared(mid-IR)to terahertz(THz)range is of interest for applications in a number of fields,from fundamental research to biology and medicine.Besides c...The generation of ultrashort high-power light sources in the mid-infrared(mid-IR)to terahertz(THz)range is of interest for applications in a number of fields,from fundamental research to biology and medicine.Besides conventional laser technology,photon deceleration in plasma wakes provides an alternative approach to the generation of ultrashort mid-IR or THz pulses.Here,we present a photon deceleration scheme for the efficient generation of ultrashort mid-IR or THz pulses by using an intense driver laser pulse with a relatively short wavelength and a signal laser pulse with a relatively long wavelength.The signal pulse trails the driver pulse with an appropriate time delay such that it sits at the front of the second wake bubble that is driven by the driver pulse.Owing to its relatively long wavelength,the signal pulse will be subjected to a large gradient of the refractive index in the plasma wake bubble.Consequently,the photon deceleration in the plasma wake becomes faster and more efficient for signal pulses with longer wavelengths.This greatly enhances the capacity and efficiency of photon deceleration in the generation of ultrashort high-power light sources in the long-wavelength IR and THz spectral ranges.展开更多
Thermochronometer data offer a powerful tool for quantifying a wide range of geologic processes,such as the deformation and erosion of mountain ranges,topographic evolution,and hydrocarbon maturation.With increasing i...Thermochronometer data offer a powerful tool for quantifying a wide range of geologic processes,such as the deformation and erosion of mountain ranges,topographic evolution,and hydrocarbon maturation.With increasing interest to quantify a wider range of complicated geologic processes,more sophisticated techniques are needed.This paper is concerned with an inverse problem method for interpreting the thermochronometer data quantitatively.Two novel models are proposed to simulate the crustal thermal fields and paleo mountain topography as a function of tectonic and surface processes.One is a heat transport model that describes the change of temperature of rocks;while the other is surface process model which explains the change of mountain topography.New computational algorithms are presented for solving the inverse problem of the coupled system of these two models.The model successfully provides a new tool for reconstructing the kinematic and the topographic history of mountains.展开更多
First evidence of a structure in the J/ψΛinvariant mass distribution is obtained from an amplitude analysis of■b-J/ψΛK-decays.The observed structure is consistent with being due to a charmonium pentaquark w...First evidence of a structure in the J/ψΛinvariant mass distribution is obtained from an amplitude analysis of■b-J/ψΛK-decays.The observed structure is consistent with being due to a charmonium pentaquark with strangeness with a significance of 3.1r including systematic uncertainties and lookelsewhere effect.Its mass and width are determined to be 4458:8±2:9t4:7-1:1 MeV and 17:3±6:5t8:0-5:7 MeV,respectively,where the quoted uncertainties are statistical and systematic.The structure is also consistent with being due to two resonances.In addition,the narrow excited■-states,N■(1690)and■(1820),are seen for the first time in a■b-decay,and their masses and widths are measured with improved precision.The analysis is performed using pp collision data corresponding to a total integrated luminosity of 9 fb-1,collected with the LHCb experiment at centre-of-mass energies of 7,8 and 13 TeV.展开更多
A first search for theΞbc+J/ψΞc+decay is performed by the LHCb experiment with a data sample of proton-proton collisions,corresponding to an integrated luminosity of 9 fb−1 recorded at centre-of-mass en...A first search for theΞbc+J/ψΞc+decay is performed by the LHCb experiment with a data sample of proton-proton collisions,corresponding to an integrated luminosity of 9 fb−1 recorded at centre-of-mass energies of 7,8,and 13 TeV.Two peaking structures are seen with a local(global)significance of 4.3(2.8)and 4.1(2.4)standard deviations at masses of 6571 and 6694 MeV/c2,respectively.Upper limits are set on theΞ+bc baryon production cross-section times the branching fraction relative to that of the B+c→J/ψD+s decay at centre-of-mass energies of 8 and 13 TeV,in theΞ+bc and in the B+c rapidity and transverse-momentum ranges from 2.0 to 4.5 and 0 to 20GeV/c,respectively.Upper limits are presented as a function of theΞ+bc mass and lifetime.展开更多
As a typical plasma-based optical element that can sustain ultra-high light intensity,plasma density gratings driven by intense laser pulses have been extensively studied for wide applications.Here,we show that the pl...As a typical plasma-based optical element that can sustain ultra-high light intensity,plasma density gratings driven by intense laser pulses have been extensively studied for wide applications.Here,we show that the plasma density grating driven by two intersecting driver laser pulses is not only nonuniform in space but also varies over time.Consequently,the probe laser pulse that passes through such a dynamic plasma density grating will be depolarized,that is,its polarization becomes spatially and temporally variable.More importantly,the laser depolarization may spontaneously take place for crossed laser beams if their polarization angles are arranged properly.The laser depolarization by a dynamic plasma density grating may find application in mitigating parametric instabilities in laser-driven inertial confinement fusion.展开更多
A search for the rare decays W+→Ds+γand Z→D0γis performed using proton-proton collision data collected by the LHCb experiment at a centre-of-mass energy of 13TeV,corresponding to an integrated luminosity ...A search for the rare decays W+→Ds+γand Z→D0γis performed using proton-proton collision data collected by the LHCb experiment at a centre-of-mass energy of 13TeV,corresponding to an integrated luminosity of 2.0fb−1.No significant signal is observed for either decay mode and upper limits on their branching fractions are set using W+→Ds+γand Z→μ+μ−decays as normalization channels.The upper limits are 6.5×10−4and 2.1×10−3at 95%confidence level for the W+→Ds+γand Z→D0γdecay modes,respectively.This is the first reported search for the Z→D0γdecay,while the upper limit on the W+→D+sγbranching fraction improves upon the previous best limit.展开更多
A search for the rare decay B0→J/ψФis performed using Pp collision data collected with the LHCb dete-ctor at centre-of-mass energies of 7,8 and 13 TeV,corresponding to an integrated luminosity of9 fb.No signific...A search for the rare decay B0→J/ψФis performed using Pp collision data collected with the LHCb dete-ctor at centre-of-mass energies of 7,8 and 13 TeV,corresponding to an integrated luminosity of9 fb.No significant signal of the decay is observed and an upper limitof 1.1x 10-7at 90%confidence level is set on the branching fraction.展开更多
The first search for the doubly heavyΩ0bcbaryon and a search for the E0bcbaryon are performed using pp collision data collected via the LHCb experiment from 2016 to 2018 at a centre-of-mass energy of 13 T...The first search for the doubly heavyΩ0bcbaryon and a search for the E0bcbaryon are performed using pp collision data collected via the LHCb experiment from 2016 to 2018 at a centre-of-mass energy of 13 TeV,corresponding to an integrated luminosity of 5.2 fb-1.The baryons are reconstructed via their decays toΛ+cπ-and E+cπ-.No significant excess is fbund for invariant masses between 6700 and 7300 MeV/c2,in a rapidity range from 2.0 to 4.5 and a transverse momentum range from 2 to 20 MeV/c.Upper limits are set on the ratio of theΩ0bcand E0bcproduction cross-section times the branching fraction toΛ+cπ-(E+cπ-)relative to that of theΛ0b(E0b)baryon,for different lifetime hypotheses,at 95%confidence level.The upper limits range from 0.5 x 10-4to 2.5 x 10-4for theΩ0bc→Λ+cπ-(E0bc→Λ+cπ-)decay,and from 1.4x 10-3to 6.9 x 10-3for theΩ0bc→E+cπ-(E0bc→E+cπ-)decay,depending on the considered mass and lifetime of theΩ0bc(E0bc)baryon.展开更多
基金supported by the National Security Academic Fund(Grant No.U2430207)the National Natural Science Foundation of China(Grant Nos.12275251,12275032,12375243,12375242,and 12035002)the Fund of the National Key Laboratory of Plasma Physics(Grant Nos.6142A04230103 and JCKYS2024212803).
摘要On laser facilities for achieving inertial confinement fusion ignition,several beams are usually bundled together and injected into the target chamber through a common port.This specific configuration could lead to laser-plasma interaction(LPI)processes that are quite different from those of a single laser beam,as well as to more options for suppressing LPI via combination of different laser smoothing techniques on the beams in a bundle.For studying LPI of a bundle of beams,a novel facility named Shenguang Octopus has been developed.Recently,the first LPI experiments have been performed by axially irradiating a gas-filled glass pipe or a gold hohlraum target with the bundled eight laser beams at an overlapped intensity of~1×1015W~cm2,producing~5-mm-long homogeneous plasmas with densities of~3×1020cm-3and temperatures of 1.2-1.5 keV.Efficient laser propagation without plasma filamentation and beam spraying has been observed via side-on X-ray images of glass pipe targets.Results from the gold hohlraum targets indicate that single-beam backward stimulated Brillouin scattering(SBS)and multibeam seeded side-SBS play major roles in the interaction,while other multibeam LPI processes expected before the experiments are not observed.Several beam smoothing techniques,such as mixed polarizations,smoothing by spectral dispersion,and multicolor mode,are demonstrated to be effective in suppressing LPI under current conditions.
基金supported by the National Natural Science Foundation of China(NSFC)under Grant Nos.52288102,52322101,92163215,52174364,52101143,U23A20542the Fundamental Research Funds for the Central Universities under Grant No.30922010202+1 种基金the 100 Talents Plan of Hebei Province under Grant No.E2020100005the Natural Science Foundation of Hebei Province under Grant No.E2022203109.
摘要Polysynthetic twinned(PST)TiAl single crystal specifically refers to a fully lamellar TiAl single crystal with parallel phase interfaces and twin interfaces grown by directional solidification.In this paper,PST single crystals with different phase ratios are obtained by annealing at specific temperatures and holding times.The results show that the diffusion rates of Ti and Al elements at various temperatures directly trigger and propel the surface recrystallization and variation in the internal phase ratio.When the temperature is lower than 1448 K,the diffusion rate of Ti is obviously higher than that of Al,which causes one denseα2recrystallized layer to form on the surface of TiAl single crystals.Meanwhile,as more Ti elements migrate to the surface,theα2phase ratio inside the TiAl single crystal thereby decreases.When the temperature exceeds 1448 K,the diffusion rate of Al gradually reverses to exceed that of Ti,which forms the surface sandwiched recrystallization dominated byγphase and simultaneously increasesα2phase ratio inside the TiAl single crystal.The variation in the two-phase ratio directly induces a significant change in the lamellae thickness,which exhibits different tensile behaviors of PST-TiAl single crystal.When theα2phase content is less than 20%,widerγlamellae make it easier for dislocations to be activated within its lamellae and continuously move across theγ/α2interfaces,thereby obtaining better tensile plasticity.As theα2phase content exceeds 30%,finerγlamellae inhibit the dislocation initiation,resulting in the fracture occurrence of TiAl single crystal before yielding.No matter how the phase ratio changes,the crack preferentially initiates withinα2lamellae.However,the crack propagation follows different paths based on variousγlamella thicknesses.The fracture mode of PST-TiAl single crystal also changes from shear fracture along slip bands within theγlamella to brittle fracture along the{1¯100}planes withinα2lamella.
基金This research was supported by the National Natural Science Foundation of China(Nos.52174364,12202201,92163215,52101143,and 91860104)Natural Science Foundation of Jiangsu Province(Nos.BK20220918,BK20212009)+3 种基金Science Center for Gas Turbine Project(P2022-A-IV-001-003)China Postdoctoral Science Foundation(No.2021M691582)the Fundamental Research Funds for the Central Universities(Nos.30922010711 and 30922010202)Open Project Program of Key Laboratory of China North Engine Research Institute(No.6142212210103).
摘要Gradient structure is emerging as an effective strategy to fabricate metals with remarkable mechanical performance,but have not been verified in intermetallic compounds for high-temperature applications.Through experiments and atomic simulations,we show that a typical intermetallic TiAl alloy with gra-dient structure has a significant strengthening effect both at room temperature and high temperatures.The room-temperature compressive strength of TiAl alloys with gradient grain obtained by additive man-ufacturing is 2.57 GPa,which is∼2.7 times as strong as that with equiaxed grain.The strengthening effect is attributed to more sessile dislocations in gradient structure caused by the intersections of mul-tiple slip systems in gradient grain.More importantly,the strengthening effect is still effective at high temperatures and the compressive strength is 1.28 GPa at 750°C.The simulation results show that this strengthening effect is due to the increased Hirth dislocation at high temperatures.This study expands the applications of TiAl alloys for load-bearing structures and provides a new strategy for improving the strength of intermetallic compounds at both room temperature and high temperatures.
基金This work was supported by the National Natural Science Foundation of China(Grant Nos.11975154,12375236,12135009,and 12275249)the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDA25050100)。
摘要The generation of ultrashort high-power light sources in the mid-infrared(mid-IR)to terahertz(THz)range is of interest for applications in a number of fields,from fundamental research to biology and medicine.Besides conventional laser technology,photon deceleration in plasma wakes provides an alternative approach to the generation of ultrashort mid-IR or THz pulses.Here,we present a photon deceleration scheme for the efficient generation of ultrashort mid-IR or THz pulses by using an intense driver laser pulse with a relatively short wavelength and a signal laser pulse with a relatively long wavelength.The signal pulse trails the driver pulse with an appropriate time delay such that it sits at the front of the second wake bubble that is driven by the driver pulse.Owing to its relatively long wavelength,the signal pulse will be subjected to a large gradient of the refractive index in the plasma wake bubble.Consequently,the photon deceleration in the plasma wake becomes faster and more efficient for signal pulses with longer wavelengths.This greatly enhances the capacity and efficiency of photon deceleration in the generation of ultrashort high-power light sources in the long-wavelength IR and THz spectral ranges.
基金The research of G.Bao,Y.Wang,and Z.Xu was supported in part by the NSF CMG grant EAR-0724527NSF grant EAR-0724656 to T.Ehlers and P.Li.
摘要Thermochronometer data offer a powerful tool for quantifying a wide range of geologic processes,such as the deformation and erosion of mountain ranges,topographic evolution,and hydrocarbon maturation.With increasing interest to quantify a wider range of complicated geologic processes,more sophisticated techniques are needed.This paper is concerned with an inverse problem method for interpreting the thermochronometer data quantitatively.Two novel models are proposed to simulate the crustal thermal fields and paleo mountain topography as a function of tectonic and surface processes.One is a heat transport model that describes the change of temperature of rocks;while the other is surface process model which explains the change of mountain topography.New computational algorithms are presented for solving the inverse problem of the coupled system of these two models.The model successfully provides a new tool for reconstructing the kinematic and the topographic history of mountains.
摘要First evidence of a structure in the J/ψΛinvariant mass distribution is obtained from an amplitude analysis of■b-J/ψΛK-decays.The observed structure is consistent with being due to a charmonium pentaquark with strangeness with a significance of 3.1r including systematic uncertainties and lookelsewhere effect.Its mass and width are determined to be 4458:8±2:9t4:7-1:1 MeV and 17:3±6:5t8:0-5:7 MeV,respectively,where the quoted uncertainties are statistical and systematic.The structure is also consistent with being due to two resonances.In addition,the narrow excited■-states,N■(1690)and■(1820),are seen for the first time in a■b-decay,and their masses and widths are measured with improved precision.The analysis is performed using pp collision data corresponding to a total integrated luminosity of 9 fb-1,collected with the LHCb experiment at centre-of-mass energies of 7,8 and 13 TeV.
基金The project support from CERN and from the national agencies:CAPES,CNPq,FAPERJ and FINEP(Brazil)MOST and NSFC(China)+18 种基金CNRS/IN2P3(France)BMBF,DFG and MPG(Germany)INFN(Italy)NWO(Netherlands)MNiSW and NCN(Poland)MEN/IFA(Romania)MICINN(Spain)SNSF and SER(Switzerland)NASU(Ukraine)STFC(United Kingdom)DOE NP and NSF(USA).We acknowledge the computing resources that are provided by CERN,IN2P3(France),KIT and DESY(Germany),INFN(Italy),SURF(Netherlands),PIC(Spain),GridPP(United Kingdom),CSCS(Switzerland),IFIN-HH(Romania),CBPF(Brazil),Polish WLCG(Poland)and NERSC(USA).Individual groups or members have received support from ARC and ARDC(Australia)Minciencias(Colombia)AvH Foundation(Germany)EPLANET,Marie Sklodowska-Curie Actions and ERC(European Union)A*MIDEX,ANR,IPhU and Labex P2IO,and Région Auvergne-RhôneAlpes(France)Key Research Program of Frontier Sciences of CAS,CAS PIFI,CAS CCEPP,Fundamental Research Funds for the Central Universities,and Sci.&Tech.Program of Guangzhou(China)GVA,XuntaGal,GENCAT and Prog.Atracción Talento,CM(Spain)SRC(Sweden)the Leverhulme Trust,the Royal Society and UKRI(United Kingdom).
摘要A first search for theΞbc+J/ψΞc+decay is performed by the LHCb experiment with a data sample of proton-proton collisions,corresponding to an integrated luminosity of 9 fb−1 recorded at centre-of-mass energies of 7,8,and 13 TeV.Two peaking structures are seen with a local(global)significance of 4.3(2.8)and 4.1(2.4)standard deviations at masses of 6571 and 6694 MeV/c2,respectively.Upper limits are set on theΞ+bc baryon production cross-section times the branching fraction relative to that of the B+c→J/ψD+s decay at centre-of-mass energies of 8 and 13 TeV,in theΞ+bc and in the B+c rapidity and transverse-momentum ranges from 2.0 to 4.5 and 0 to 20GeV/c,respectively.Upper limits are presented as a function of theΞ+bc mass and lifetime.
基金supported by the National Natural Science Foundation of China(Grant Nos.11975154,11991074,12005287 and 12135009)the Strategic Priority Research Program of Chinese Academy of Sciences(Grant Nos.XDA25050100 and XDA25010100)+1 种基金the Presidential Foundation of the China Academy of Engineering Physics(Grant No.YZJJLX2016008)the Science Challenge Project(Grant No.TZ2018005).
摘要As a typical plasma-based optical element that can sustain ultra-high light intensity,plasma density gratings driven by intense laser pulses have been extensively studied for wide applications.Here,we show that the plasma density grating driven by two intersecting driver laser pulses is not only nonuniform in space but also varies over time.Consequently,the probe laser pulse that passes through such a dynamic plasma density grating will be depolarized,that is,its polarization becomes spatially and temporally variable.More importantly,the laser depolarization may spontaneously take place for crossed laser beams if their polarization angles are arranged properly.The laser depolarization by a dynamic plasma density grating may find application in mitigating parametric instabilities in laser-driven inertial confinement fusion.
摘要A search for the rare decays W+→Ds+γand Z→D0γis performed using proton-proton collision data collected by the LHCb experiment at a centre-of-mass energy of 13TeV,corresponding to an integrated luminosity of 2.0fb−1.No significant signal is observed for either decay mode and upper limits on their branching fractions are set using W+→Ds+γand Z→μ+μ−decays as normalization channels.The upper limits are 6.5×10−4and 2.1×10−3at 95%confidence level for the W+→Ds+γand Z→D0γdecay modes,respectively.This is the first reported search for the Z→D0γdecay,while the upper limit on the W+→D+sγbranching fraction improves upon the previous best limit.
基金support from AvH Foundation(Germany)EPLANET,Marie Sk lodowska-Curie Actions and ERC(European Union)+11 种基金A*MIDEXANRLabex P2IOOCEVURégion Auvergne-Rh?ne-Alpes(France)Key Research Program of Frontier Sciences of CASCAS PIFIThousand Talents ProgramSci.&Tech.Program of Guangzhou(China)RFBR,RSF and Yandex LLC(Russia)GVA,Xunta Gal and GENCAT(Spain)the Royal Society and the Leverhulme Trust(United Kingdom)。
摘要A search for the rare decay B0→J/ψФis performed using Pp collision data collected with the LHCb dete-ctor at centre-of-mass energies of 7,8 and 13 TeV,corresponding to an integrated luminosity of9 fb.No significant signal of the decay is observed and an upper limitof 1.1x 10-7at 90%confidence level is set on the branching fraction.
基金CAPES,CNPq,FAPERJ and FINEP(Brazil)MOST and NSFC(China)+18 种基金CNRS/IN2P3(France)BMBF,DFG,MPG(Germany)INFN(Italy)NWO(Netherlands)MNiSW,NCN(Poland)MEN/IFA(Romania)MSHE(Russia)MICINN(Spain)SNSF,SER(Switzerland)NASU(Ukraine)STFC(United Kingdom)DOE NP,NSF(USA).We acknowledge the computing resources that are provided by CERN,IN2P3(France),KIT and DESY(Germany),INFN(Italy),SURF(Netherlands),PIC(Spain),GridPP(United Kingdom),RRCKI and Yandex LLC(Russia),CSCS(Switzerland),IFIN-HH(Romania),CBPF(Brazil),PL-GRID(Poland)and NERSC(USA)AvH Foundation(Germany)EPLANET,Marie Sklodowska-Curie Actions and ERC(European Union)A*MIDEX,ANR,Labex P2IO and OCEVU,Region Auvergne-Rhdne-Alpes(France)Key Research Program of Frontier Sciences of CAS,CAS PIFI,CAS CCEPP,Fundamental Research Funds for the Central Universities,and Sci.Tech.Program of Guangzhou(China)RFBR,RSF and Yandex LLC(Russia)GVA,XuntaGal,GENCAT(Spain)the Leverhulme Trust,the Royal Society and UKRI(United Kingdom)。
摘要The first search for the doubly heavyΩ0bcbaryon and a search for the E0bcbaryon are performed using pp collision data collected via the LHCb experiment from 2016 to 2018 at a centre-of-mass energy of 13 TeV,corresponding to an integrated luminosity of 5.2 fb-1.The baryons are reconstructed via their decays toΛ+cπ-and E+cπ-.No significant excess is fbund for invariant masses between 6700 and 7300 MeV/c2,in a rapidity range from 2.0 to 4.5 and a transverse momentum range from 2 to 20 MeV/c.Upper limits are set on the ratio of theΩ0bcand E0bcproduction cross-section times the branching fraction toΛ+cπ-(E+cπ-)relative to that of theΛ0b(E0b)baryon,for different lifetime hypotheses,at 95%confidence level.The upper limits range from 0.5 x 10-4to 2.5 x 10-4for theΩ0bc→Λ+cπ-(E0bc→Λ+cπ-)decay,and from 1.4x 10-3to 6.9 x 10-3for theΩ0bc→E+cπ-(E0bc→E+cπ-)decay,depending on the considered mass and lifetime of theΩ0bc(E0bc)baryon.