LHCb

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 ${\mathrm{\Xi }}_c^{+}{\pi }^{-}{\pi }^{+}$ spectrum is investigated using proton-proton collisions at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of $5.4{\mathrm{fb}}^{-1}$ , collected by the LHCb experiment during 2016–2018. Four states are observed with high significance, and their masses and widths are measured to be $m[{\mathrm{\Xi }}_c(2815{)}^{+}]=2816.65\pm 0.03\pm 0.03\pm 0.23\mathrm{MeV}$ , $\mathrm{\Gamma }[{\mathrm{\Xi }}_c(2815{)}^{+}]=2.07\pm 0.08\pm 0.12\mathrm{MeV}$ , $m[{\mathrm{\Xi }}_c(2923{)}^{+}]=2922.8\pm 0.3\pm 0.5\pm 0.2\mathrm{MeV}$ , $\mathrm{\Gamma }[{\mathrm{\Xi }}_c(2923{)}^{+}]=5.3\pm 0.9\pm 1.4\mathrm{MeV}$ , $m[{\mathrm{\Xi }}_c(2970{)}^{+}]=2968.6\pm 0.5\pm 0.5\pm 0.2\mathrm{MeV}$ , $\mathrm{\Gamma }[{\mathrm{\Xi }}_c(2970{)}^{+}]=31.7\pm 1.7\pm 1.9\mathrm{MeV}$ , $[{\mathrm{\Xi }}_c(3080{)}^{+}]=3076.8\pm 0.7\pm 1.3\pm 0.2\mathrm{MeV}$ , $\mathrm{\Gamma }[{\mathrm{\Xi }}_c(3080{)}^{+}]=6.8\pm 2.3\pm 0.9\mathrm{MeV}$ , where the uncertainties are statistical, systematic, and due to the limited precision on the ${\mathrm{\Xi }}_c^{+}$ mass, respectively. The ${\mathrm{\Xi }}_c(2923{)}^{+}$ baryon is observed for the first time, and is consistent with being the isospin partner of the previously observed ${\mathrm{\Xi }}_c(2923{)}^0$ state. Most of the measured parameters are more precise than existing world averages.

Abstract:

Volume 3 of the FCC Feasibility Report presents studies related to civil engineering, the development of a project implementation scenario, and environmental and sustainability aspects. The report details the iterative improvements made to the civil engineering concepts since 2018, taking into account subsurface conditions, accelerator and experiment requirements, and territorial considerations. It outlines a technically feasible and economically viable civil engineering configuration that serves as the baseline for detailed subsurface investigations, construction design, cost estimation, and project implementation planning. Additionally, the report highlights ongoing subsurface investigations in key areas to support the development of an improved 3D subsurface model of the region. The report describes the development of the project scenario based on the ‘avoid-reduce-compensate’ iterative optimisation approach. The reference scenario balances optimal physics performance with territorial compatibility, implementation risks, and costs. Environmental field investigations covering almost 600 hectares of terrain—including numerous urban, economic, social, and technical aspects—confirmed the project’s technical feasibility and contributed to the preparation of essential input documents for the formal project authorisation phase. The summary also highlights the initiation of public dialogue as part of the authorisation process. The results of a comprehensive socio-economic impact assessment, which included significant environmental effects, are presented. Even under the most conservative and stringent conditions, a positive benefit-cost ratio for the FCC-ee is obtained. Finally, the report provides a summary of the studies conducted to document the current state of the environment.