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arXiv · 2001.00851

First observation of excited $Ω_b^-$ states

LHCb collaboration·R. Aaij·C. Abellán Beteta·T. Ackernley·B. Adeva·M. Adinolfi·H. Afsharnia·C. A. Aidala·S. Aiola·Z. Ajaltouni·S. Akar·P. Albicocco·J. Albrecht·F. Alessio·M. Alexander·A. Alfonso Albero·G. Alkhazov·P. Alvarez Cartelle·A. A. Alves Jr·S. Amato·Y. Amhis·L. An·L. Anderlini·G. Andreassi·M. Andreotti·F. Archilli·J. Arnau Romeu·A. Artamonov·M. Artuso·K. Arzymatov·E. Aslanides·M. Atzeni·B. Audurier·S. Bachmann·J. J. Back·S. Baker·V. Balagura·W. Baldini·A. Baranov·R. J. Barlow·S. Barsuk·W. Barter·M. Bartolini·F. Baryshnikov·G. Bassi·V. Batozskaya·B. Batsukh·A. Battig·A. Bay·M. Becker·F. Bedeschi·I. Bediaga·A. Beiter·L. J. Bel·V. Belavin·S. Belin·V. Bellee·K. Belous·I. Belyaev·G. Bencivenni·E. Ben-Haim·S. Benson·S. Beranek·A. Berezhnoy·R. Bernet·D. Berninghoff·H. C. Bernstein·C. Bertella·E. Bertholet·A. Bertolin·C. Betancourt·F. Betti·M. O. Bettler·Ia. Bezshyiko·S. Bhasin·J. Bhom·M. S. Bieker·S. Bifani·P. Billoir·A. Bizzeti·M. Bjørn·M. P. Blago·T. Blake·F. Blanc·S. Blusk·D. Bobulska·V. Bocci·O. Boente Garcia·T. Boettcher·A. Boldyrev·A. Bondar·N. Bondar·S. Borghi·M. Borisyak·M. Borsato·J. T. Borsuk·T. J. V. Bowcock·C. Bozzi·M. J. Bradley·S. Braun
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Abstract

We report four narrow peaks in the $Ξ_b^0K^-$ mass spectrum obtained using $pp$ collisions at center-of-mass energies of 7, 8 and 13 TeV, corresponding to a total integrated luminosity of 9 fb$^{-1}$ recorded by the LHCb experiment. Referring to these states by their mass, the mass values are \begin{align*} m(Ω_b(6316)^-) &= 6315.64\pm0.31\pm0.07\pm0.50 {\rm MeV}, \\ m(Ω_b(6330)^-) &= 6330.30\pm0.28\pm0.07\pm0.50 {\rm MeV}, \\ m(Ω_b(6340)^-) &= 6339.71\pm0.26\pm0.05\pm0.50 {\rm MeV}, \\ m(Ω_b(6350)^-) &= 6349.88\pm0.35\pm0.05\pm0.50 {\rm MeV}, \end{align*}where the uncertainties are statistical, systematic and the last is due to the knowledge of the $Ξ_b^0$ mass. The natural widths of the three lower mass states are consistent with zero, and the 90% confidence-level upper limits are determined to be ${Γ(Ω_b(6316)^-)<2.8}$ MeV, ${Γ(Ω_b(6330)^-)<3.1}$ MeV and ${Γ(Ω_b(6340)^-)<1.5}$ MeV. The natural width of the $Ω_b(6350)^-$ peak is $1.4^{+1.0}_{-0.8}\pm0.1$ MeV, which is 2.5$σ$ from zero and corresponds to an upper limit of 2.8 MeV. The peaks have local significances ranging from 3.6$σ$ to 7.2$σ$. After accounting for the look-elsewhere effect, the significances of the $Ω_b(6316)^-$ and $Ω_b(6330)^-$ peaks are reduced to 2.1$σ$ and 2.6$σ$ respectively, while the two higher mass peaks exceed 5$σ$. The observed peaks are consistent with expectations for excited $Ω_b^-$ resonances.

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LHCb collaboration, R. Aaij, C. Abellán Beteta, T. Ackernley, B. Adeva, M. Adinolfi, H. Afsharnia, C. A. Aidala, S. Aiola, Z. Ajaltouni, S. Akar, P. Albicocco, J. Albrecht, F. Alessio, M. Alexander, A. Alfonso Albero, G. Alkhazov, P. Alvarez Cartelle, A. A. Alves Jr, S. Amato, Y. Amhis, L. An, L. Anderlini, G. Andreassi, M. Andreotti, F. Archilli, J. Arnau Romeu, A. Artamonov, M. Artuso, K. Arzymatov, E. Aslanides, M. Atzeni, B. Audurier, S. Bachmann, J. J. Back, S. Baker, V. Balagura, W. Baldini, A. Baranov, R. J. Barlow, S. Barsuk, W. Barter, M. Bartolini, F. Baryshnikov, G. Bassi, V. Batozskaya, B. Batsukh, A. Battig, A. Bay, M. Becker, F. Bedeschi, I. Bediaga, A. Beiter, L. J. Bel, V. Belavin, S. Belin, V. Bellee, K. Belous, I. Belyaev, G. Bencivenni, E. Ben-Haim, S. Benson, S. Beranek, A. Berezhnoy, R. Bernet, D. Berninghoff, H. C. Bernstein, C. Bertella, E. Bertholet, A. Bertolin, C. Betancourt, F. Betti, M. O. Bettler, Ia. Bezshyiko, S. Bhasin, J. Bhom, M. S. Bieker, S. Bifani, P. Billoir, A. Bizzeti, M. Bjørn, M. P. Blago, T. Blake, F. Blanc, S. Blusk, D. Bobulska, V. Bocci, O. Boente Garcia, T. Boettcher, A. Boldyrev, A. Bondar, N. Bondar, S. Borghi, M. Borisyak, M. Borsato, J. T. Borsuk, T. J. V. Bowcock, C. Bozzi, M. J. Bradley, S. Braun. 2020-02-25. First observation of excited $Ω_b^-$ states. https://doi.org/10.1103/physrevlett.124.082002

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