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Register a new userDetermination of the forward slope in $p~p$ and $bar p~p$ elastic scattering up to LHC energy
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In the analysis of experimental data on $p p$ (or $bar p p$) elastic differential cross section it is customary to define an average forward slope $b$ in the form $exp{(-b|t|)}$, where $t$ is the momentum transfer. Taking as working example the results of experiments at Tevatron and SPS, we will show with the help of the impact picture approach, that this simplifying assumption hides interesting information on the complex non-flip scattering amplitude, and that the slope $b$ is not a constant. We investigate the variation of this slope parameter, including a model-independent way to extract this information from an accurate measurement of the elastic differential cross section. An extension of our results to the LHC energy domain is presented in view of future experiments.
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We calculate various azimuthal angle distributions for three jets produced in the forward rapidity region with transverse momenta $p_T>20,mathrm{GeV}$ in proton-proton (p-p) and proton-lead (p-Pb) collisions at center of mass energy $5.02,,mathrm{TeV}$. We use the multi-parton extension of the so-called small-$x$ Improved Transverse Momentum Dependent factorization (ITMD). We study effects related to change from the standard $k_T$-factorization to ITMD factorization as well as changes as one goes from p-p collision to p-Pb. We observe rather large differences in the distribution when we change the factorization approach, which allows to both improve the small-$x$ TMD gluon distributions as well as validate and improve the factorization approach. We also see significant depletion of the nuclear modification ratio, indicating a possibility of searches for saturation effects using trijet final states in a more exclusive way than for dijets.
Provided the enhancement in the $p bar{p}$ spectrum in radiative decay $J/psi to gamma p bar{p}$ observed by the BES collaboration is due to an existence of a $p bar{p}$ molecular state, we calculate its binding energy and lifetime in the linear $sigma$ model. We consider a possibility that the enhancement is due to a $p bar p$ resonance which is in either S-wave or P-wave structure and compare our results with the data.
Exact analytical forms of solutions for Dispersion Relations for Amplitudes and Dispersion Relations for Slopes are applied in the analysis of pp and $rm {p bar p}$ scattering data in the forward range at energies below $sqrt(s)approx 30 GeV$. As inputs for the energy dependence of the imaginary part, use is made of analytic form for the total cross sections and for parameters of the $t$ dependence of the imaginary parts, with exponential and linear factors. A structure for the $t$ dependence of the real amplitude is written, with slopes $B_R$ and a linear factor $rho-mu_R t$ that allows compatibility of the data with the predictions from dispersion relations for the derivatives of the real amplitude at the origin. A very precise description is made of all $dsigma/dt$ data, with regular energy dependence of all quantities. It is shown that a revision of previous calculations of total cross sections, slopes and $rho$ parameters in the literatures is necessary, and stressed that only determinations based on $dsigma/dt$ data covering sufficient $t$ range using appropriate forms of amplitudes can be considered as valid.
The first observation of the decay $eta_{c}(2S) to p bar p$ is reported using proton-proton collision data corresponding to an integrated luminosity of $3.0rm , fb^{-1}$ recorded by the LHCb experiment at centre-of-mass energies of 7 and 8 TeV. The $eta_{c}(2S)$ resonance is produced in the decay $B^{+} to [cbar c] K^{+}$. The product of branching fractions normalised to that for the $J/psi$ intermediate state, ${cal R}_{eta_{c}(2S)}$, is measured to be begin{align*} {cal R}_{eta_{c}(2S)}equivfrac{{mathcal B}(B^{+} to eta_{c}(2S) K^{+}) times {mathcal B}(eta_{c}(2S) to p bar p)}{{mathcal B}(B^{+} to J/psi K^{+}) times {mathcal B}(J/psito p bar p)} =~& (1.58 pm 0.33 pm 0.09)times 10^{-2}, end{align*} where the first uncertainty is statistical and the second systematic. No signals for the decays $B^{+} to X(3872) (to p bar p) K^{+}$ and $B^{+} to psi(3770) (to p bar p) K^{+}$ are seen, and the 95% confidence level upper limits on their relative branching ratios are % found to be ${cal R}_{X(3872)}<0.25times10^{-2}$ and ${cal R}_{psi(3770))}<0.10$. In addition, the mass differences between the $eta_{c}(1S)$ and the $J/psi$ states, between the $eta_{c}(2S)$ and the $psi(2S)$ states, and the natural width of the $eta_{c}(1S)$ are measured as begin{align*} M_{J/psi} - M_{eta_{c}(1S)} =~& 110.2 pm 0.5 pm 0.9 rm , MeV, M_{psi(2S)} -M_{eta_{c}(2S)} =~ & 52.5 pm 1.7 pm 0.6 rm , MeV, Gamma_{eta_{c}(1S)} =~& 34.0 pm 1.9 pm 1.3 rm , MeV. end{align*}
In this work, the triangle singularity mechanism is investigated in the $psi(2S) to p bar{p} eta / p bar{p} pi^0$ process. The triangle loop composed by $J/psi$, $eta$ and $p$ has a singularity in the physical kinematic range for the $psi(2S) to p bar{p} eta / p bar{p} pi^0$ process, and it would generate a very narrow peak in the invariant mass spectrum of $peta (pi)$ around $1.56387$ GeV, which is far away from both the threshold and relative resonances. In these processes, all the involved vertices are constrained by the experimental data. Thus, we can make a precise model independent prediction here. It turns out that the peak in the $peta$ invariant mass spectrum is visible, while it is very small in the $ppi^0$ invariant mass spectrum. We expect this effect shown in $p bar{p} eta$ final state can be observed by the Beijing Spectrometer (BESIII) and Super Tau-Charm Facility (STCF) in the future.
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