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1. Observation of the $${{{\Lambda }} _{\text {b}}^{{0}}} \rightarrow {{\text {J}/\uppsi }} {{{\Xi }} ^{{-}}} {{\text {K}} ^{{+}}} $$ decay

   https://doi.org/10.1140/epjc/s10052-024-13114-9  

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

   Abstract Using proton–proton collision data corresponding to an integrated luminosity of$$140\hbox { fb}^{-1}$$ $140{\text{fb}}^{-1}$collected by the CMS experiment at$$\sqrt{s}= 13\,\text {Te}\hspace{-.08em}\text {V} $$ $\sqrt{s}=13\text{Te}\text{V}$, the$${{{\Lambda }} _{\text {b}}^{{0}}} \rightarrow {{\text {J}/\uppsi }} {{{\Xi }} ^{{-}}} {{\text {K}} ^{{+}}} $$ ${\Lambda }_{\text{b}}^0\to \text{J}/\psi {\Xi }^{-}{\text{K}}^{+}$decay is observed for the first time, with a statistical significance exceeding 5 standard deviations. The relative branching fraction, with respect to the$${{{\Lambda }} _{\text {b}}^{{0}}} \rightarrow {{{\uppsi }} ({2\textrm{S}})} {{\Lambda }} $$ ${\Lambda }_{\text{b}}^0\to \psi \left(2\text{S}\right)\Lambda$decay, is measured to be$$\mathcal {B}({{{\Lambda }} _{\text {b}}^{{0}}} \rightarrow {{\text {J}/\uppsi }} {{{\Xi }} ^{{-}}} {{\text {K}} ^{{+}}} )/\mathcal {B}({{{\Lambda }} _{\text {b}}^{{0}}} \rightarrow {{{\uppsi }} ({2\textrm{S}})} {{\Lambda }} ) = [3.38\pm 1.02\pm 0.61\pm 0.03]\%$$ $B({\Lambda }_{\text{b}}^0\to \text{J}/\psi {\Xi }^{-}{\text{K}}^{+})/B({\Lambda }_{\text{b}}^0\to \psi \left(2\text{S}\right)\Lambda )=[3.38\pm 1.02\pm 0.61\pm 0.03]\%$, where the first uncertainty is statistical, the second is systematic, and the third is related to the uncertainties in$$\mathcal {B}({{{\uppsi }} ({2\textrm{S}})} \rightarrow {{\text {J}/\uppsi }} {{{\uppi }} ^{{+}}} {{{\uppi }} ^{{-}}} )$$ $B(\psi \left(2\text{S}\right)\to \text{J}/\psi {\pi }^{+}{\pi }^{-})$and$$\mathcal {B}({{{\Xi }} ^{{-}}} \rightarrow {{\Lambda }} {{{\uppi }} ^{{-}}} )$$ $B({\Xi }^{-}\to \Lambda {\pi }^{-})$. 

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2. 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 ($$-0.96<0.04$$ $-0.96<y<0.04$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. 

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3. Measurement of non-prompt $${{\textrm{D}}^{0}}$$-meson elliptic flow in Pb–Pb collisions at $$\sqrt{s_{\textrm{NN}}} = 5.02$$ TeV

   https://doi.org/10.1140/epjc/s10052-023-12259-3  

   Acharya, S; Adamová, D; Aglieri_Rinella, G; Agnello, M; Agrawal, N; Ahammed, Z; Ahmad, S; Ahn, S U; Ahuja, I; Akindinov, A; et al (December 2023, The European Physical Journal C)

   Abstract The elliptic flow$$(v_2)$$ $\left(v_2\right)$of$${\textrm{D}}^{0}$$ ${\text{D}}^0$mesons from beauty-hadron decays (non-prompt$${\textrm{D}}^{0})$$ ${\text{D}}^0)$was measured in midcentral (30–50%) Pb–Pb collisions at a centre-of-mass energy per nucleon pair$$\sqrt{s_{\textrm{NN}}} = 5.02$$ $\sqrt{s_{\text{NN}}}=5.02$ TeV with the ALICE detector at the LHC. The$${\textrm{D}}^{0}$$ ${\text{D}}^0$mesons were reconstructed at midrapidity$$(|y|<0.8)$$ $\left(\right|y|<0.8)$from their hadronic decay$$\mathrm {D^0 \rightarrow K^-\uppi ^+}$$ $D^0\to K^{-}{\pi }^{+}$, in the transverse momentum interval$$2< p_{\textrm{T}} < 12$$ $2<p_{\text{T}}<12$ GeV/c. The result indicates a positive$$v_2$$ $v_2$for non-prompt$${{\textrm{D}}^{0}}$$ ${\text{D}}^0$mesons with a significance of 2.7$$\sigma $$ $\sigma$. The non-prompt$${{\textrm{D}}^{0}}$$ ${\text{D}}^0$-meson$$v_2$$ $v_2$is lower than that of prompt non-strange D mesons with 3.2$$\sigma $$ $\sigma$significance in$$2< p_\textrm{T} < 8~\textrm{GeV}/c$$ $2<p_{\text{T}}<8\text{GeV}/c$, and compatible with the$$v_2$$ $v_2$of beauty-decay electrons. Theoretical calculations of beauty-quark transport in a hydrodynamically expanding medium describe the measurement within uncertainties. 

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4. 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. 

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5. Measurement of the production cross section of prompt $$\Xi ^0_{\textrm{c}}$$ baryons in p–Pb collisions at $$\sqrt{s_{{\textrm{NN}}}}=5.02$$ TeV

   https://doi.org/10.1140/epjc/s10052-024-13531-w  

   Acharya, S; Adamová, D; Agarwal, A; Aglieri_Rinella, G; Aglietta, L; Agnello, M; Agrawal, N; Ahammed, Z; Ahmad, S; Ahn, S U; et al (January 2025, The European Physical Journal C)

   Abstract The transverse momentum ($$p_{\textrm{T}}$$ $p_{\text{T}}$) differential production cross section of the promptly produced charm-strange baryon$$\mathrm {\Xi _{c}^{0}}$$ ${\Xi }_c^0$(and its charge conjugate$$\overline{\mathrm {\Xi _{c}^{0}}}$$ $\overline{{\Xi }_c^0}$) is measured at midrapidity via its hadronic decay into$$\mathrm{\pi ^{+}}\Xi ^{-}$$ ${\pi }^{+}{\Xi }^{-}$in p–Pb collisions at a centre-of-mass energy per nucleon–nucleon collision$$\sqrt{s_{\textrm{NN}}}~=~5.02$$ $\sqrt{s_{\text{NN}}}=5.02$ TeV with the ALICE detector at the LHC. The$$\mathrm {\Xi _{c}^{0}}$$ ${\Xi }_c^0$nuclear modification factor ($$R_{\textrm{pPb}}$$ $R_{\text{pPb}}$), calculated from the cross sections in pp and p–Pb collisions, is presented and compared with the$$R_{\textrm{pPb}}$$ $R_{\text{pPb}}$of$$\mathrm {\Lambda _{c}^{+}}$$ ${\Lambda }_c^{+}$baryons. The ratios between the$$p_{\textrm{T}}$$ $p_{\text{T}}$-differential production cross section of$$\mathrm {\Xi _{c}^{0}}$$ ${\Xi }_c^0$baryons and those of$$\mathrm {D^0}$$ $D^0$mesons and$$\mathrm {\Lambda _{c}^{+}}$$ ${\Lambda }_c^{+}$baryons are also reported and compared with results at forward and backward rapidity from the LHCb Collaboration. The measurements of the production cross section of prompt$$\Xi ^0_\textrm{c}$$ ${\Xi }_{\text{c}}^0$baryons are compared with a model based on perturbative QCD calculations of charm-quark production cross sections, which includes only cold nuclear matter effects in p–Pb collisions, and underestimates the measurement by a factor of about 50. This discrepancy is reduced when the data is compared with a model that includes string formation beyond leading-colour approximation or in which hadronisation is implemented via quark coalescence. The$$p_{\textrm{T}}$$ $p_{\text{T}}$-integrated cross section of prompt$$\Xi ^0_\textrm{c}$$ ${\Xi }_{\text{c}}^0$-baryon production at midrapidity extrapolated down to$$p_{\textrm{T}}$$ $p_{\text{T}}$= 0 is also reported. These measurements offer insights and constraints for theoretical calculations of the hadronisation process. Additionally, they provide inputs for the calculation of the charm production cross section in p–Pb collisions at midrapidity. 

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