Measurement of charged particle spectra in minimum-bias events from proton-proton collisions at root s =13 TeV

Pseudorapidity, transverse momentum, and multiplicity distributions are measured in the pseudorapidity range vertical bar eta vertical bar 0.5 GeV in proton-proton collisions at a center-of-mass energy of root s = 13 TeV. Measurements are presented in three different event categories. The most inclusive of the categories corresponds to an inelastic pp data set, while the other two categories are exclusive subsets of the inelastic sample that are either enhanced or depleted in single diffractive dissociation events. The measurements are compared to predictions from Monte Carlo event generators used to describe high-energy hadronic interactions in collider and cosmic-ray physics.Peer reviewe

Evidence for X(3872) in Pb-Pb Collisions and Studies of its Prompt Production at sNN\sqrt {s_{NN}}=5.02 TeV

The first evidence for X(3872) production in relativistic heavy ion collisions is reported. The $X(3872)$ production is studied in lead-lead (Pb-Pb) collisions at a center-of-mass energy of $\sqrt {s_{NN}}$ 5.02 TeV per nucleon pair, using the decay chain $X(3872) → J/ψ π^+ π^− → μ^+ μ^- π^+ π^−$. The data were recorded with the CMS detector in 2018 and correspond to an integrated luminosity of 1.7 nb$^{-1}$. The measurement is performed in the rapidity and transverse momentum ranges $|y|<$ 1.6 and 15$< p_T <$ 50 GeV/c. The significance of the inclusive $X(3872)$ signal is 4.2 standard deviations. The prompt $X(3872)$ to $ψ2S$ yield ratio is found to be $ρ^{Pb-Pb} =1.08±0.49(stat)±0.52(syst)$, to be compared with typical values of 0.1 for pp collisions. This result provides a unique experimental input to theoretical models of the $X(3872)$ production mechanism, and of the nature of this exotic state

Measurement of single-diffractive dijet production in proton-proton collisions at s=\sqrt{s} =s​= 8 TeV with the CMS and TOTEM experiments

Measurements are presented of the single-diffractive dijet cross section and the diffractive cross section as a function of the proton fractional momentum loss $\xi$ and the four-momentum transfer squared t. Both processes ${\text{ p }{}{}} {\text{ p }{}{}} \rightarrow {\text{ p }{}{}} {\text{ X }}$ and ${\text{ p }{}{}} {\text{ p }{}{}} \rightarrow {\text{ X }} {\text{ p }{}{}}$, i.e. with the proton scattering to either side of the interaction point, are measured, where ${\text{ X }}$ includes at least two jets; the results of the two processes are averaged. The analyses are based on data collected simultaneously with the CMS and TOTEM detectors at the LHC in proton–proton collisions at $\sqrt{s} = 8\,\text {Te}\text {V}$ during a dedicated run with $\beta ^{*} = 90\,\text {m}$ at low instantaneous luminosity and correspond to an integrated luminosity of $37.5{\,\text {nb}^{-1}}$. The single-diffractive dijet cross section $\sigma ^{{\text{ p }{}{}} {\text{ X }}}_{\mathrm {jj}}$, in the kinematic region $\xi 40\,\text {Ge}\text {V}$, and pseudorapidity $|\eta | < 4.4$, is 21.7 \pm 0.9\,\text {(stat)} \,^{+3.0}_{-3.3}\,\text {(syst)} \pm 0.9\,\text {(lumi)} \,\text {nb} . The ratio of the single-diffractive to inclusive dijet yields, normalised per unit of $\xi$, is presented as a function of x, the longitudinal momentum fraction of the proton carried by the struck parton. The ratio in the kinematic region defined above, for x values in the range $-2.9 \le \log _{10} x \le -1.6$, is $R = (\sigma ^{{\text{ p }{}{}} {\text{ X }}}_{\mathrm {jj}}/\Delta \xi )/\sigma _{\mathrm {jj}} = 0.025 \pm 0.001\,\text {(stat)} \pm 0.003\,\text {(syst)}$, where $\sigma ^{{\text{ p }{}{}} {\text{ X }}}_{\mathrm {jj}}$ and $\sigma _{\mathrm {jj}}$ are the single-diffractive and inclusive dijet cross sections, respectively. The results are compared with predictions from models of diffractive and nondiffractive interactions. Monte Carlo predictions based on the HERA diffractive parton distribution functions agree well with the data when corrected for the effect of soft rescattering between the spectator partons

Erratum to: Measurement of single-diffractive dijet production in proton–proton collisions at s=8 TeV\sqrt{s} = 8\,\text {Te}\text {V} with the CMS and TOTEM experiments

The original PDF version of this article was revised as theOpen Access license text was missing and the funding note“Funded by SCOAP3” as well. The original article has been corrected