Measurement of the production cross section for a W boson in association with a charm quark in proton–proton collisions at $$\sqrt{s} = 13\,\hbox {TeV}$$
Annotatsiya
Abstract The strange quark content of the proton is probed through the measurement of the production cross section for a W boson and a charm (c) quark in proton–proton collisions at a center-of-mass energy of 13 $$\,\text {Te}\hspace{-.08em}\text {V}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mspace/> <mml:mtext>Te</mml:mtext> <mml:mspace/> <mml:mtext>V</mml:mtext> </mml:mrow> </mml:math> . The analysis uses a data sample corresponding to a total integrated luminosity of 138 $$\,\text {fb}^{-1}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mspace/> <mml:msup> <mml:mtext>fb</mml:mtext> <mml:mrow> <mml:mo>-</mml:mo> <mml:mn>1</mml:mn> </mml:mrow> </mml:msup> </mml:mrow> </mml:math> collected with the CMS detector at the LHC. The W bosons are identified through their leptonic decays to an electron or a muon, and a neutrino. Charm jets are tagged using the presence of a muon or a secondary vertex inside the jet. The $$\hbox {W}+\hbox {c}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mtext>W</mml:mtext> <mml:mo>+</mml:mo> <mml:mtext>c</mml:mtext> </mml:mrow> </mml:math> production cross section and the cross section ratio $$R_\textrm{c}^{\pm }= \sigma ({\hbox {W}}^{+}+\bar{\text {c}})/\sigma (\hbox {W}^{-}+{\textrm{c}})$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:msubsup> <mml:mi>R</mml:mi> <mml:mtext>c</mml:mtext> <mml:mo>±</mml:mo> </mml:msubsup> <mml:mo>=</mml:mo> <mml:mi>σ</mml:mi> <mml:mrow> <mml:mo>(</mml:mo> <mml:msup> <mml:mrow> <mml:mtext>W</mml:mtext> </mml:mrow> <mml:mo>+</mml:mo> </mml:msup> <mml:mo>+</mml:mo> <mml:mover> <mml:mrow> <mml:mtext>c</mml:mtext> </mml:mrow> <mml:mrow> <mml:mo>¯</mml:mo> </mml:mrow> </mml:mover> <mml:mo>)</mml:mo> </mml:mrow> <mml:mo>/</mml:mo> <mml:mi>σ</mml:mi> <mml:mrow> <mml:mo>(</mml:mo> <mml:msup> <mml:mtext>W</mml:mtext> <mml:mo>-</mml:mo> </mml:msup> <mml:mo>+</mml:mo> <mml:mtext>c</mml:mtext> <mml:mo>)</mml:mo> </mml:mrow> </mml:mrow> </mml:math> are measured inclusively and differentially as functions of the transverse momentum and the pseudorapidity of the lepton originating from the W boson decay. The precision of the measurements is improved with respect to previous studies, reaching 1% in $$R_\textrm{c}^{\pm }= 0.950 \pm 0.005\,\text {(stat)} \pm 0.010 \,\text {(syst)} $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:msubsup> <mml:mi>R</mml:mi> <mml:mtext>c</mml:mtext> <mml:mo>±</mml:mo> </mml:msubsup> <mml:mo>=</mml:mo> <mml:mn>0.950</mml:mn> <mml:mo>±</mml:mo> <mml:mn>0.005</mml:mn> <mml:mspace/> <mml:mtext>(stat)</mml:mtext> <mml:mo>±</mml:mo> <mml:mn>0.010</mml:mn> <mml:mspace/> <mml:mtext>(syst)</mml:mtext> </mml:mrow> </mml:math> . The measurements are compared with theoretical predictions up to next-to-next-to-leading order in perturbative quantum chromodynamics.
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