More Like this

1. Charm fragmentation fractions and $$\mathbf {c\overline{c}}$$ cross section in p–Pb collisions at $$\mathbf {\sqrt{s _{NN}}=5.02 TeV}$$

   https://doi.org/10.1140/epjc/s10052-024-13394-1  

   Acharya, S; Adamová, D; Agarwal, A; Aglieri_Rinella, G; Aglietta, L; Agnello, M; Agrawal, N; Ahammed, Z; Ahmad, S; Ahn, S U; et al (December 2024, The European Physical Journal C)

   Abstract The total charm-quark production cross section per unit of rapidity$$\textrm{d}\sigma ({{\textrm{c}}\overline{\textrm{c}}})/\textrm{d}y$$ $\text{d}\sigma \left(\text{c}\overline{\text{c}}\right)/\text{d}y$ , and the fragmentation fractions of charm quarks to different charm-hadron species$$f(\textrm{c}\rightarrow {\textrm{h}}_{\textrm{c}})$$ $f(\text{c}\to {\text{h}}_{\text{c}})$ , are measured for the first time in p–Pb collisions at$$\sqrt{s_\textrm{NN}} = 5.02~\text {Te}\hspace{-1.00006pt}\textrm{V} $$ $\sqrt{s_{\text{NN}}}=5.02\text{Te}\text{V}$ at midrapidity ($$-0.96 $-0.96<y<0.04$ in the centre-of-mass frame) using data collected by ALICE at the CERN LHC. The results are obtained based on all the available measurements of prompt production of ground-state charm-hadron species:$$\textrm{D}^{0}$$ ${\text{D}}^0$ ,$$\textrm{D}^{+}$$ ${\text{D}}^{+}$ ,$$\textrm{D}_\textrm{s}^{+}$$ ${\text{D}}_{\text{s}}^{+}$ , and$$\mathrm {J/\psi }$$ $J/\psi$ mesons, and$$\Lambda _\textrm{c}^{+}$$ ${\Lambda }_{\text{c}}^{+}$ and$$\Xi _\textrm{c}^{0}$$ ${\Xi }_{\text{c}}^0$ baryons. The resulting cross section is$$ \textrm{d}\sigma ({{\textrm{c}}\overline{\textrm{c}}})/\textrm{d}y =219.6 \pm 6.3\;(\mathrm {stat.}) {\;}_{-11.8}^{+10.5}\;(\mathrm {syst.}) {\;}_{-2.9}^{+8.3}\;(\mathrm {extr.})\pm 5.4\;(\textrm{BR})\pm 4.6\;(\mathrm {lumi.}) \pm 19.5\;(\text {rapidity shape})+15.0\;(\Omega _\textrm{c}^{0})\;\textrm{mb} $$ $\text{d}\sigma \left(\text{c}\overline{\text{c}}\right)/\text{d}y=219.6\pm 6.3\left(\mathrm{stat}.\right)_{-11.8}^{+10.5}\left(\mathrm{syst}.\right)_{-2.9}^{+8.3}\left(\mathrm{extr}.\right)\pm 5.4\left(\text{BR}\right)\pm 4.6\left(\mathrm{lumi}.\right)\pm 19.5\left(\text{rapidity shape}\right)+15.0\left({\Omega }_{\text{c}}^0\right)\text{mb}$ , which is consistent with a binary scaling of pQCD calculations from pp collisions. The measured fragmentation fractions are compatible with those measured in pp collisions at$$\sqrt{s} = 5.02$$ $\sqrt{s}=5.02$ and 13 TeV, showing an increase in the relative production rates of charm baryons with respect to charm mesons in pp and p–Pb collisions compared with$$\mathrm {e^{+}e^{-}}$$ $e^{+}{e}^{-}$ and$$\mathrm {e^{-}p}$$ $e^{-}p$ collisions. The$$p_\textrm{T}$$ $p_{\text{T}}$ -integrated nuclear modification factor of charm quarks,$$R_\textrm{pPb}({\textrm{c}}\overline{\textrm{c}})= 0.91 \pm 0.04\;\mathrm{(stat.)} ^{+0.08}_{-0.09}\;\mathrm{(syst.)} ^{+0.05}_{-0.03}\;\mathrm{(extr.)} \pm 0.03\;\mathrm{(lumi.)}$$ $R_{\text{pPb}}\left(\text{c}\overline{\text{c}}\right)=0.91\pm 0.04{(\mathrm{stat}.)}_{-0.09}^{+0.08}{(\mathrm{syst}.)}_{-0.03}^{+0.05}(\mathrm{extr}.)\pm 0.03(\mathrm{lumi}.)$ , is found to be consistent with unity and with theoretical predictions including nuclear modifications of the parton distribution functions. 

   more » « less
2. Measurement of the production cross section for a W boson in association with a charm quark in proton–proton collisions at $$\sqrt{s} = 13\,\hbox {TeV}$$

   https://doi.org/10.1140/epjc/s10052-023-12258-4  

   Tumasyan, A; Adam, W; Andrejkovic, J W; Bergauer, T; Chatterjee, S; Damanakis, K; Dragicevic, M; Valle, A_Escalante Del; Hussain, P S; Jeitler, M; et al (January 2024, The European Physical Journal C)

   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$$\,\text {Te}\hspace{-.08em}\text {V}$$ $\text{Te}\text{V}$ . The analysis uses a data sample corresponding to a total integrated luminosity of 138$$\,\text {fb}^{-1}$$ ${\text{fb}}^{-1}$ 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$$\hbox {W}+\hbox {c}$$ $\text{W}+\text{c}$ production cross section and the cross section ratio$$R_\textrm{c}^{\pm }= \sigma ({\hbox {W}}^{+}+\bar{\text {c}})/\sigma (\hbox {W}^{-}+{\textrm{c}})$$ $R_{\text{c}}^{\pm }=\sigma ({\text{W}}^{+}+\overline{\text{c}})/\sigma ({\text{W}}^{-}+\text{c})$ 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$$R_\textrm{c}^{\pm }= 0.950 \pm 0.005\,\text {(stat)} \pm 0.010 \,\text {(syst)} $$ $R_{\text{c}}^{\pm }=0.950\pm 0.005\text{(stat)}\pm 0.010\text{(syst)}$ . The measurements are compared with theoretical predictions up to next-to-next-to-leading order in perturbative quantum chromodynamics. 

   more » « less
3. Measurement of CP violation in B0 → D+D− and $$ {\textrm{B}}_{\textrm{s}}^0 $$ → $$ {\textrm{D}}_{\textrm{s}}^{+}{\textrm{D}}_{\textrm{s}}^{-} $$ decays

   https://doi.org/10.1007/JHEP01(2025)061  

   Aaij, R; Abdelmotteleb, A_S W; Abellan_Beteta, C; Abudinén, F; Ackernley, T; Adefisoye, A A; Adeva, B; Adinolfi, M; Adlarson, P; Agapopoulou, C; et al (January 2025, Journal of High Energy Physics)

   A<sc>bstract</sc> A time-dependent, flavour-tagged measurement ofCPviolation is performed withB⁰→ D⁺D⁻and$$ {B}_s^0 $$ $B_s^0$ →$$ {D}_s^{+}{D}_s^{-} $$ $D_s^{+}{D}_s^{-}$ decays, using data collected by the LHCb detector in proton-proton collisions at a centre-of-mass energy of 13 TeV corresponding to an integrated luminosity of 6 fb⁻¹. InB⁰→ D⁺D⁻decays theCP-violation parameters are measured to be$$ {\displaystyle \begin{array}{c}{S}_{D^{+}{D}^{-}}=-0.552\pm 0.100\left(\textrm{stat}\right)\pm 0.010\left(\textrm{syst}\right),\\ {}{C}_{D^{+}{D}^{-}}=0.128\pm 0.103\left(\textrm{stat}\right)\pm 0.010\left(\textrm{syst}\right).\end{array}} $$ $\begin{array}{c}{S}_{D^{+}{D}^{-}}=-0.552\pm 0.100\left(\text{stat}\right)\pm 0.010\left(\text{syst}\right),\\ C_{D^{+}{D}^{-}}=0.128\pm 0.103\left(\text{stat}\right)\pm 0.010\left(\text{syst}\right).\end{array}$ In$$ {B}_s^0 $$ $B_s^0$ →$$ {D}_s^{+}{D}_s^{-} $$ $D_s^{+}{D}_s^{-}$ decays theCP-violating parameter formulation in terms ofϕ_sand|λ|results in$$ {\displaystyle \begin{array}{c}{\phi}_s=-0.086\pm 0.106\left(\textrm{stat}\right)\pm 0.028\left(\textrm{syst}\right)\textrm{rad},\\ {}\mid {\lambda}_{D_s^{+}{D}_s^{-}}\mid =1.145\pm 0.126\left(\textrm{stat}\right)\pm 0.031\left(\textrm{syst}\right).\end{array}} $$ $\begin{array}{c}{\varphi }_s=-0.086\pm 0.106\left(\text{stat}\right)\pm 0.028\left(\text{syst}\right)\mathrm{rad},\\ \mid {\lambda }_{D_s^{+}{D}_s^{-}}\mid =1.145\pm 0.126\left(\text{stat}\right)\pm 0.031\left(\text{syst}\right).\end{array}$ These results represent the most precise single measurement of theCP-violation parameters in their respective channels. For the first time in a single measurement,CPsymmetry is observed to be violated inB⁰→ D⁺D⁻decays with a significance exceeding six standard deviations. 

   more » « less
4. Measurement of the $$ {\varOmega}_c^0 $$ and $$ {\Xi}_c^0 $$ baryon lifetimes using hadronic b-baryon decays

   https://doi.org/10.1007/JHEP09(2025)157  

   Aaij, R; Abdelmotteleb, A_S W; Abellan_Beteta, C; Abudinén, F; Ackernley, T; Adefisoye, A A; Adeva, B; Adinolfi, M; Adlarson, P; Agapopoulou, C; et al (September 2025, Journal of High Energy Physics)

   A<sc>bstract</sc> The lifetimes of the$$ {\varOmega}_c^0 $$ ${\Omega }_c^0$ and$$ {\Xi}_c^0 $$ ${\Xi }_c^0$ baryons are measured using appcollision dataset collected by the LHCb experiment, corresponding to an integrated luminosity of 9 fb⁻¹. The charm baryons are produced in the fully reconstructed decay chains$$ {\varOmega}_b^{-}\to {\varOmega}_c^0\left(\to p{K}^{-}{K}^{-}{\pi}^{+}\right){\pi}^{-} $$ ${\Omega }_b^{-}\to {\Omega }_c^0\left(\to p{K}^{-}{K}^{-}{\pi }^{+}\right){\pi }^{-}$ and$$ {\Xi}_b^{-}\to {\Xi}_c^0\left(\to p{K}^{-}{K}^{-}{\pi}^{+}\right){\pi}^{-} $$ ${\Xi }_b^{-}\to {\Xi }_c^0\left(\to p{K}^{-}{K}^{-}{\pi }^{+}\right){\pi }^{-}$ . The measurement uses topologically and kinematically similarB⁻→D⁰(→K⁻K⁺π⁻π⁺)π⁻decays for normalisation. The measured lifetimes are$$ {\displaystyle \begin{array}{c}{\tau}_{\varOmega_c^0}=276.3\pm 19.4\left(\textrm{stat}\right)\pm 1.8\left(\textrm{syst}\right)\pm 0.7\left({\tau}_{D^0}\right)\textrm{fs},\\ {}{\tau}_{\Xi_c^0}=149.2\pm 2.5\left(\textrm{stat}\right)\pm 0.9\left(\textrm{syst}\right)\pm 0.4\ \left({\tau}_{D^0}\right)\textrm{fs},\end{array}} $$ $\begin{array}{c}{\tau }_{{\Omega }_c^0}=276.3\pm 19.4\left(\text{stat}\right)\pm 1.8\left(\text{syst}\right)\pm 0.7\left({\tau }_{D^0}\right)\mathrm{fs},\\ {\tau }_{{\Xi }_c^0}=149.2\pm 2.5\left(\text{stat}\right)\pm 0.9\left(\text{syst}\right)\pm 0.4\left({\tau }_{D^0}\right)\mathrm{fs},\end{array}$ where the first uncertainty is statistical, the second systematic and the third due to the uncertainty of theD⁰lifetime. These results are consistent with previous measurements performed by the LHCb experiment. 

   more » « less
5. Amplitude analysis of $$B^0 \rightarrow \eta _c(1S) K^+ \pi ^- $$ decays

   https://doi.org/10.1140/epjc/s10052-026-15474-w  

   Aaij, R; Abdelmotteleb, ASW; Beteta, C Abellan; Abudinén, F; Ackernley, T; Adefisoye, A A; Adeva, B; Adinolfi, M; Adlarson, P; Agapopoulou, C; et al (May 2026, The European Physical Journal C)

   Abstract An amplitude analysis of the$${{{B} ^0} \!\rightarrow {\eta _{c}} (1S) {{K} ^+} {{\pi } ^-}} $$ $B^0\to {\eta }_c\left(1S\right)K^{+}{\pi }^{-}$ decays with$${\eta _{c}} (1S) \rightarrow {p} {\overline{{p}}} $$ ${\eta }_c\left(1S\right)\to p\overline{p}$ is performed using a sample corresponding to an integrated luminosity of 9$$\,\text {fb} ^{-1}$$ ${\text{fb}}^{-1}$ of$$p $$ $p$ $$p $$ $p$ collision data collected by the LHCb detector at centre-of-mass energies of$$\sqrt{s}$$ $\sqrt{s}$ = 7, 8 and 13$$\,\text {Te\hspace{-1.00006pt}V}$$ $\text{Te}\text{V}$ . The data are described with a model including only intermediate contributions from known$${K} ^{*0}$$ $K_{}^{\ast 0}$ resonances. Evidence for an exotic resonance in the$${\eta _{c}} (1S) {{\pi } ^-} $$ ${\eta }_c\left(1S\right){\pi }^{-}$ system, reported in a previous analysis of this decay channel, is not confirmed. The inclusive branching fraction of the$${{B} ^0} \rightarrow {\eta _{c}} (1S) {{K} ^+} {{\pi } ^-} $$ $B^0\to {\eta }_c\left(1S\right)K^{+}{\pi }^{-}$ decays is measured to be$$\begin{aligned}&\mathcal {B}({{B} ^0} \rightarrow {\eta _{c}} (1S) {{K} ^+} {{\pi } ^-}) \\&\quad = (5.82 \pm 0.20 \pm 0.23 \pm 0.55) \times 10^{-4}, \end{aligned}$$ $\begin{array}{cc}& B(B^0\to {\eta }_c\left(1S\right)K^{+}{\pi }^{-})\\ & =(5.82\pm 0.20\pm 0.23\pm 0.55)\times {10}^{-4},\end{array}$ where the first uncertainty is statistical, the second systematic, and the third arises from the limited knowledge of external branching fractions. 

   more » « less