Observation of a new baryon state in the $$ {\Lambda}_{\mathrm{b}}^0{\pi}^{+}{\pi}^{-} $$ mass spectrum
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. Álvarez Cartelle, A. A. Alves, S. Amato, Y. Amhis, L. An, L. Anderlini, G. Andreassi, M. Andreotti, F. Archilli, A. Artamonov, M. Artuso, Kenenbek Arzymatov, E. Aslanides, M. Atzeni, B. Audurier, S. Bachmann, J. J. Back, S. Baker, V. Balagura, W. Baldini, А. В. Баранов, R. J. Barlow, S. Barsuk, W. Barter, M. Bartolini, F. Baryshnikov, J. M. Basels, 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. Bellée, 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, Michele Piero Blago, T. Blake, F. Blanc, S. Blusk, D. Bobulska, V. Bocci, O. Boente García, 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, A. Brea Rodríguez
Abstract
A bstract A new baryon state is observed in the $$ {\Lambda}_{\mathrm{b}}^0{\pi}^{+}{\pi}^{-} $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msubsup> <mml:mi>Λ</mml:mi> <mml:mi>b</mml:mi> <mml:mn>0</mml:mn> </mml:msubsup> <mml:msup> <mml:mi>π</mml:mi> <mml:mo>+</mml:mo> </mml:msup> <mml:msup> <mml:mi>π</mml:mi> <mml:mo>−</mml:mo> </mml:msup> </mml:math> mass spectrum with high significance using a data sample of pp collisions, collected with the LHCb detector at centre-of-mass energies $$ \sqrt{s} $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msqrt> <mml:mi>s</mml:mi> </mml:msqrt> </mml:math> = 7 , 8 and 13 TeV, corresponding to an integrated luminosity of 9 fb − 1 . The mass and natural width of the new state are measured to be $$ {\displaystyle \begin{array}{l}m=6072.3\pm 2.9\pm 0.6\pm 0.2\ \mathrm{MeV},\\ {}\Gamma =72\pm 11\pm 2\ \mathrm{MeV},\end{array}} $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mtable> <mml:mtr> <mml:mtd> <mml:mi>m</mml:mi> <mml:mo>=</mml:mo> <mml:mn>6072.3</mml:mn> <mml:mo>±</mml:mo> <mml:mn>2.9</mml:mn> <mml:mo>±</mml:mo> <mml:mn>0.6</mml:mn> <mml:mo>±</mml:mo> <mml:mn>0.2</mml:mn> <mml:mspace/> <mml:mi>MeV</mml:mi> <mml:mo>,</mml:mo> </mml:mtd> </mml:mtr> <mml:mtr> <mml:mtd> <mml:mi>Γ</mml:mi> <mml:mo>=</mml:mo> <mml:mn>72</mml:mn> <mml:mo>±</mml:mo> <mml:mn>11</mml:mn> <mml:mo>±</mml:mo> <mml:mn>2</mml:mn> <mml:mspace/> <mml:mi>MeV</mml:mi> <mml:mo>,</mml:mo> </mml:mtd> </mml:mtr> </mml:mtable> </mml:math> where the first uncertainty is statistical and the second systematic. The third uncertainty for the mass is due to imprecise knowledge of the $$ {\Lambda}_{\mathrm{b}}^0 $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msubsup> <mml:mi>Λ</mml:mi> <mml:mi>b</mml:mi> <mml:mn>0</mml:mn> </mml:msubsup> </mml:math> baryon mass. The new state is consistent with the first radial excitation of the $$ {\Lambda}_{\mathrm{b}}^0 $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msubsup> <mml:mi>Λ</mml:mi> <mml:mi>b</mml:mi> <mml:mn>0</mml:mn> </mml:msubsup> </mml:math> baryon, the Λ b (2S) 0 resonance. Updated measurements of the masses and the upper limits on the natural widths of the previously observed Λ b (5912) 0 and Λ b (5920) 0 states are also reported.