91̽»¨

Abstract:

A study of Λb0 and Ξb0 baryon decays to the final states pKS0π− and pKS0K− is performed using pp collision data collected by the LHCb experiment, corresponding to an integrated luminosity of 9 fb−1. The decays Λb0→pKS0K− and Ξb0→pKS0K− are observed for the first time, with significances reaching eight standard deviations. The branching fractions and integrated CP asymmetries are measured for the Λb0→pKS0π−, Λb0→pKS0K−, and Ξb0→pKS0K− decays. For the decay Λb0→pKS0π−, the CP asymmetries are measured in different regions of the Dalitz plot. No evidence of CP violation is observed.

Abstract:

A time-integrated angular analysis of the decay Bs0→J/ψK¯∗8920, with J/ψ → μ+μ− and K¯∗8920→K−π+, is presented. The analysis employs a sample of proton-proton collision data collected by the LHCb experiment during 2015–2018 at a centre-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 6 fb−1. A simultaneous maximum-likelihood fit is performed to the angular distributions in bins of the K−π+ mass. This fit yields measurements of the CP-averaged polarisation fractions and CP asymmetries for the P-wave component of the K−π+ system. The longitudinal and parallel polarisation fractions are determined to be f0 = 0.534 ± 0.012 ± 0.009 and f|| = 0.211 ± 0.014 ± 0.005, respectively, where the first uncertainty is statistical and the second is systematic. The CP asymmetries are measured with 3–7% precision and are found to be consistent with zero. These measurements, along with an updated determination of the branching fraction relative to the B0 → J/ψK*0 decay, are combined with previous LHCb results, providing the most precise values for these observables to date.

Abstract:

<jats:p>The study of meson pairs produced with quantum correlations gives direct access to parameters that are challenging to measure in other systems. In this Letter, the existence of quantum correlations due to charge-conjugation symmetry <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"><a:mi>C</a:mi></a:math> are demonstrated in <c:math xmlns:c="http://www.w3.org/1998/Math/MathML" display="inline"><c:mi>D</c:mi><c:mover accent="true"><c:mi>D</c:mi><c:mo stretchy="true">¯</c:mo></c:mover></c:math> pairs produced through the processes <g:math xmlns:g="http://www.w3.org/1998/Math/MathML" display="inline"><g:msup><g:mi>e</g:mi><g:mo>+</g:mo></g:msup><g:msup><g:mi>e</g:mi><g:mo>−</g:mo></g:msup><g:mo stretchy="false">→</g:mo><g:mrow><g:mi>D</g:mi><g:mover accent="true"><g:mi>D</g:mi><g:mo stretchy="true">¯</g:mo></g:mover></g:mrow></g:math>, <l:math xmlns:l="http://www.w3.org/1998/Math/MathML" display="inline"><l:msup><l:mi>e</l:mi><l:mo>+</l:mo></l:msup><l:msup><l:mi>e</l:mi><l:mo>−</l:mo></l:msup><l:mo stretchy="false">→</l:mo><l:mrow><l:msup><l:mi>D</l:mi><l:mo>*</l:mo></l:msup><l:mover accent="true"><l:mi>D</l:mi><l:mo stretchy="true">¯</l:mo></l:mover></l:mrow></l:math>, and <q:math xmlns:q="http://www.w3.org/1998/Math/MathML" display="inline"><q:msup><q:mi>e</q:mi><q:mo>+</q:mo></q:msup><q:msup><q:mi>e</q:mi><q:mo>−</q:mo></q:msup><q:mo stretchy="false">→</q:mo><q:mrow><q:msup><q:mi>D</q:mi><q:mo>*</q:mo></q:msup><q:mrow><q:msup><q:mover accent="true"><q:mi>D</q:mi><q:mo stretchy="true">¯</q:mo></q:mover><q:mo>*</q:mo></q:msup></q:mrow></q:mrow></q:math>, where the lack of charge superscripts refers to an admixture of neutral-charm-meson particle and antiparticle states, using <v:math xmlns:v="http://www.w3.org/1998/Math/MathML" display="inline"><v:mn>7.13</v:mn><v:mtext> </v:mtext><v:mtext> </v:mtext><v:msup><v:mi>fb</v:mi><v:mrow><v:mo>−</v:mo><v:mn>1</v:mn></v:mrow></v:msup></v:math> of <x:math xmlns:x="http://www.w3.org/1998/Math/MathML" display="inline"><x:msup><x:mi>e</x:mi><x:mo>+</x:mo></x:msup><x:msup><x:mi>e</x:mi><x:mo>−</x:mo></x:msup></x:math> collision data collected by the BESIII experiment between center-of-mass energies of 4.13–4.23 GeV. Processes with either <z:math xmlns:z="http://www.w3.org/1998/Math/MathML" display="inline"><z:mi>C</z:mi></z:math>-even or <bb:math xmlns:bb="http://www.w3.org/1998/Math/MathML" display="inline"><bb:mi>C</bb:mi></bb:math>-odd constraints are identified and separated. A procedure is presented that harnesses the entangled production process to enable measurements of <db:math xmlns:db="http://www.w3.org/1998/Math/MathML" display="inline"><db:msup><db:mi>D</db:mi><db:mn>0</db:mn></db:msup></db:math>-meson hadronic parameters. This Letter provides the first confirmation of quantum correlations in <fb:math xmlns:fb="http://www.w3.org/1998/Math/MathML" display="inline"><fb:msup><fb:mi>e</fb:mi><fb:mo>+</fb:mo></fb:msup><fb:msup><fb:mi>e</fb:mi><fb:mo>−</fb:mo></fb:msup><fb:mo stretchy="false">→</fb:mo><fb:mi>X</fb:mi><fb:mrow><fb:mi>D</fb:mi><fb:mover accent="true"><fb:mi>D</fb:mi><fb:mo stretchy="true">¯</fb:mo></fb:mover></fb:mrow></fb:math> processes and the first observation of a <kb:math xmlns:kb="http://www.w3.org/1998/Math/MathML" display="inline"><kb:mi>C</kb:mi></kb:math>-even constrained <mb:math xmlns:mb="http://www.w3.org/1998/Math/MathML" display="inline"><mb:mi>D</mb:mi><mb:mover accent="true"><mb:mi>D</mb:mi><mb:mo stretchy="true">¯</mb:mo></mb:mover></mb:math> system. The procedure is applied to measure <qb:math xmlns:qb="http://www.w3.org/1998/Math/MathML" display="inline"><qb:msubsup><qb:mi>δ</qb:mi><qb:mrow><qb:mi>K</qb:mi><qb:mi>π</qb:mi></qb:mrow><qb:mi>D</qb:mi></qb:msubsup></qb:math>, the strong phase between the <sb:math xmlns:sb="http://www.w3.org/1998/Math/MathML" display="inline"><sb:mrow><sb:msup><sb:mrow><sb:mi>D</sb:mi></sb:mrow><sb:mrow><sb:mn>0</sb:mn></sb:mrow></sb:msup><sb:mo stretchy="false">→</sb:mo><sb:msup><sb:mrow><sb:mi>K</sb:mi></sb:mrow><sb:mrow><sb:mo>−</sb:mo></sb:mrow></sb:msup><sb:msup><sb:mrow><sb:mi>π</sb:mi></sb:mrow><sb:mrow><sb:mo>+</sb:mo></sb:mrow></sb:msup></sb:mrow></sb:math> and <vb:math xmlns:vb="http://www.w3.org/1998/Math/MathML" display="inline"><vb:mrow><vb:mrow><vb:msup><vb:mrow><vb:mover accent="true"><vb:mrow><vb:mi>D</vb:mi></vb:mrow><vb:mrow><vb:mo stretchy="true">¯</vb:mo></vb:mrow></vb:mover></vb:mrow><vb:mrow><vb:mn>0</vb:mn></vb:mrow></vb:msup></vb:mrow><vb:mo stretchy="false">→</vb:mo><vb:msup><vb:mrow><vb:mi>K</vb:mi></vb:mrow><vb:mrow><vb:mo>−</vb:mo></vb:mrow></vb:msup><vb:msup><vb:mrow><vb:mi>π</vb:mi></vb:mrow><vb:mrow><vb:mo>+</vb:mo></vb:mrow></vb:msup></vb:mrow></vb:math> decay amplitudes, which results in the determination of <ac:math xmlns:ac="http://www.w3.org/1998/Math/MathML" display="inline"><ac:mrow><ac:msubsup><ac:mrow><ac:mi>δ</ac:mi></ac:mrow><ac:mrow><ac:mi>K</ac:mi><ac:mi>π</ac:mi></ac:mrow><ac:mrow><ac:mi>D</ac:mi></ac:mrow></ac:msubsup><ac:mo>=</ac:mo><ac:mo stretchy="false">(</ac:mo><ac:msubsup><ac:mrow><ac:mn>192.8</ac:mn></ac:mrow><ac:mrow><ac:mo>−</ac:mo><ac:mn>12.4</ac:mn><ac:mo>−</ac:mo><ac:mn>2.4</ac:mn></ac:mrow><ac:mrow><ac:mo>+</ac:mo><ac:mn>11.0</ac:mn><ac:mo>+</ac:mo><ac:mn>1.9</ac:mn></ac:mrow></ac:msubsup><ac:mo stretchy="false">)</ac:mo><ac:mo>°</ac:mo></ac:mrow></ac:math>. The potential for measurements of other hadronic decay parameters and charm mixing with these and future datasets is also discussed.</jats:p>

Abstract:

<jats:p>A novel measurement technique of strong-phase differences between the decay amplitudes of <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"><a:msup><a:mi>D</a:mi><a:mn>0</a:mn></a:msup></a:math> and <c:math xmlns:c="http://www.w3.org/1998/Math/MathML" display="inline"><c:mrow><c:msup><c:mrow><c:mover accent="true"><c:mrow><c:mi>D</c:mi></c:mrow><c:mrow><c:mo accent="true" stretchy="true">¯</c:mo></c:mrow></c:mover></c:mrow><c:mrow><c:mn>0</c:mn></c:mrow></c:msup></c:mrow></c:math> mesons is introduced which exploits quantum-correlated <h:math xmlns:h="http://www.w3.org/1998/Math/MathML" display="inline"><h:mrow><h:mi>D</h:mi><h:mrow><h:mover accent="true"><h:mrow><h:mi>D</h:mi></h:mrow><h:mrow><h:mo stretchy="true">¯</h:mo></h:mrow></h:mover></h:mrow></h:mrow></h:math> pairs produced by <l:math xmlns:l="http://www.w3.org/1998/Math/MathML" display="inline"><l:msup><l:mi>e</l:mi><l:mo>+</l:mo></l:msup><l:msup><l:mi>e</l:mi><l:mo>−</l:mo></l:msup></l:math> collisions at energies above the <n:math xmlns:n="http://www.w3.org/1998/Math/MathML" display="inline"><n:mi>ψ</n:mi><n:mo stretchy="false">(</n:mo><n:mn>3770</n:mn><n:mo stretchy="false">)</n:mo></n:math> production threshold, where <r:math xmlns:r="http://www.w3.org/1998/Math/MathML" display="inline"><r:mrow><r:mi>D</r:mi><r:mover accent="true"><r:mrow><r:mi>D</r:mi></r:mrow><r:mrow><r:mo stretchy="true">¯</r:mo></r:mrow></r:mover></r:mrow></r:math> pairs are produced in both even and odd eigenstates of the charge-conjugation symmetry. Employing this technique, the first determination of a <v:math xmlns:v="http://www.w3.org/1998/Math/MathML" display="inline"><v:mrow><v:msup><v:mrow><v:mi>D</v:mi></v:mrow><v:mrow><v:mn>0</v:mn></v:mrow></v:msup><v:mi>–</v:mi><v:msup><v:mrow><v:mover accent="true"><v:mrow><v:mi>D</v:mi></v:mrow><v:mrow><v:mo accent="true" stretchy="true">¯</v:mo></v:mrow></v:mover></v:mrow><v:mrow><v:mn>0</v:mn></v:mrow></v:msup></v:mrow></v:math> relative strong phase is reported with such data samples. The strong-phase difference between <ab:math xmlns:ab="http://www.w3.org/1998/Math/MathML" display="inline"><ab:mrow><ab:msup><ab:mrow><ab:mi>D</ab:mi></ab:mrow><ab:mrow><ab:mn>0</ab:mn></ab:mrow></ab:msup><ab:mo stretchy="false">→</ab:mo><ab:msup><ab:mrow><ab:mi>K</ab:mi></ab:mrow><ab:mrow><ab:mo>−</ab:mo></ab:mrow></ab:msup><ab:msup><ab:mrow><ab:mi>π</ab:mi></ab:mrow><ab:mrow><ab:mo>+</ab:mo></ab:mrow></ab:msup></ab:mrow></ab:math> and <db:math xmlns:db="http://www.w3.org/1998/Math/MathML" display="inline"><db:mrow><db:msup><db:mrow><db:mover accent="true"><db:mrow><db:mi>D</db:mi></db:mrow><db:mrow><db:mo accent="true" stretchy="true">¯</db:mo></db:mrow></db:mover></db:mrow><db:mrow><db:mn>0</db:mn></db:mrow></db:msup><db:mo stretchy="false">→</db:mo><db:msup><db:mrow><db:mi>K</db:mi></db:mrow><db:mrow><db:mo>−</db:mo></db:mrow></db:msup><db:msup><db:mrow><db:mi>π</db:mi></db:mrow><db:mrow><db:mo>+</db:mo></db:mrow></db:msup></db:mrow></db:math> decays, <jb:math xmlns:jb="http://www.w3.org/1998/Math/MathML" display="inline"><jb:msubsup><jb:mi>δ</jb:mi><jb:mrow><jb:mi>K</jb:mi><jb:mi>π</jb:mi></jb:mrow><jb:mi>D</jb:mi></jb:msubsup></jb:math>, is measured to be <lb:math xmlns:lb="http://www.w3.org/1998/Math/MathML" display="inline"><lb:msubsup><lb:mi>δ</lb:mi><lb:mrow><lb:mi>K</lb:mi><lb:mi>π</lb:mi></lb:mrow><lb:mi>D</lb:mi></lb:msubsup><lb:mo>=</lb:mo><lb:msup><lb:mrow><lb:mo stretchy="false">(</lb:mo><lb:msubsup><lb:mn>192.8</lb:mn><lb:mrow><lb:mo>−</lb:mo><lb:mn>12.4</lb:mn><lb:mo>−</lb:mo><lb:mn>2.4</lb:mn></lb:mrow><lb:mrow><lb:mo>+</lb:mo><lb:mn>11.0</lb:mn><lb:mo>+</lb:mo><lb:mn>1.9</lb:mn></lb:mrow></lb:msubsup><lb:mo stretchy="false">)</lb:mo></lb:mrow><lb:mo>∘</lb:mo></lb:msup></lb:math>, using a dataset corresponding to an integrated luminosity of <pb:math xmlns:pb="http://www.w3.org/1998/Math/MathML" display="inline"><pb:mn>7.13</pb:mn><pb:mtext> </pb:mtext><pb:mtext> </pb:mtext><pb:msup><pb:mi>fb</pb:mi><pb:mrow><pb:mo>−</pb:mo><pb:mn>1</pb:mn></pb:mrow></pb:msup></pb:math> collected at center-of-mass energies between 4.13–4.23 GeV by the BESIII experiment.</jats:p>

Abstract:

The first dedicated $Z$ -boson mass measurement at the LHC with $Z→{\mathrm{μ}}^{+}{\mathrm{μ}}^{−}$ decays is reported. The dataset uses proton-proton collisions at a center-of-mass energy of 13 TeV, recorded in 2016 by the LHCb experiment, and corresponds to an integrated luminosity of $1.7{\mathrm{fb}}^{−1}$ . A template fit to the ${\mathrm{μ}}^{+}{\mathrm{μ}}^{−}$ mass distribution yields the following result for the $Z$ -boson mass: $m_Z=91,185.7Â\pm 8.3Â\pm 3.9\mathrm{MeV}$ , where the first uncertainty is statistical and the second systematic. This result is consistent with previous measurements and predictions from global electroweak fits.