Scaling amplitudes describing $pp$ elastic scattering differential cross-sections in the dip-bump region of momentum transfer at the LHC have been recently derived~\cite{scaling}. We check that the same scaling is verified by the $p\bar p$ cross-section at the highest energy of the Tevatron. Applying the general"energy to phase"relation for a given signature, coming from the analiticity properties inherent to the S-Matrix formalism~\cite{chew}, we derive the scaling amplitude with positive signature (i.e. the Pomeron). Fitting the $pp$ differential cross-sections measured by the TOTEM collaboration leads to some tension with data in the experimental dip observed at moderate momentum transfer. Concentrating the study to the dip/bump region, we are able to determine a contribution of a negative signature amplitude (i.e. the Odderon) leading to a parameter free prediction for the $p\bar p$ differential cross-section which is in agreement with the D0 data. The extraction of the Odderon amplitude in both modulus and phase is then performed and discussed.
We present a global two-channel Flatt\'e amplitude analysis of the hidden-charm pentaquark candidates observed by the LHCb collaboration in the J/{\psi}p invariant-mass spectrum using the Run 1+2 dataset. We simultaneously fit the three pentaquark amplitudes to the full spectrum, including a polynomial background and complex coupling phases. The scattering length and effective range are extracted from the fitted amplitudes using the effective range expansion, with uncertainties determined through non-parametric bootstrap resampling. While real couplings yield scattering parameters compatible with a molecular interpretation, this conclusion becomes less robust when coupling phases are included. We further find that interference effects are important for the closely spaced Pc(4440)+ and Pc(4457)+ states, demonstrating the limitations of the incoherent-sum approximation.
A. Likéné, P. P. Hebbar, Alexis Franck Rothen et al.· 0 citations
Geometric scaling was conjectured and observed at the ISR more than 50 years ago. We argue that it still holds at the LHC. We show that the dip-bump structures of the differential elastic cross-sections exhibit a remarkable regularity, namely that the ratio of the bump to dip positions is constant from 23 GeV to 13 TeV. Using crossing symmetry, analicity and the optical theorem, we identify the imaginary and real parts of the scattering amplitude. This allows us to compute the $\rho$ parameter and the ratio of the bump to dip values of the differential $pp$ cross-section. Finally, we discuss the energy dependence of the total elastic cross-section as compared to the total cross-section, and the violation of geometrical scaling outside the dip-bump region at the LHC.
Michał Praszałowicz· Proceedings of Proceedings o...· 0 citations
We report the measurement of the four-fold differential cross section of deeply virtual Compton scattering (DVCS) on the proton using a longitudinally polarized 10.6 GeV CEBAF electron beam incident on a liquid-hydrogen target with the CLAS12 detector. The analysis provides 1312 data points, expanding the measured phase space in the valence quark region, 0.06<$x_B$<0.58, 1.00<$Q^2$<5.76 GeV$^2$, and 0.11<$|t|$<1.00 GeV$^2$. DVCS cross section measurements directly constrain the real part of the DVCS amplitude through its interference with the Bethe-Heitler process, making them essential inputs to global extractions of the Compton Form Factors (CFFs), particularly the dominant CFF $H$. These data improve sensitivity to these observables and can contribute to future determinations of the proton's internal mechanical structure.
S. Lee, T. Hayward, L. Elouadrhiri et al.· 0 citations
We present the details of a dispersive method to construct the amplitudes for hadronic multibody $B$ decays based on the universality of pairwise hadronic final-state interactions at low invariant masses. This approach allows us to split the amplitude into source terms controlled by phenomenological parameters and final-state interactions, governed by the precise knowledge of two-body dynamics, both resonant and non-resonant. As a concrete application, we make use of the well-determined low-energy pion-pion ($\pi\pi$) interactions to understand the enhanced localized CP violation observed in $B^{\pm}\rightarrow K^{\pm}\pi^+\pi^-$. Fitting only angle-integrated CP-asymmetry data, the method successfully predicts the Dalitz plot differential distribution of events and of the CP asymmetry in the low-energy region. This allows for a better understanding of the large localized CP asymmetry recently reported by LHCb, which is shown not to be driven by an absolute enhancement of CP-violating effects, but by a suppression of the CP-conserving part resulting from the interplay of several partial waves. Moreover, we show that the widely-neglected non-resonant isospin-2 contributions play an essential role in the description of CP violation in this system. The method can be straightforwardly adapted to other multibody decays, where final-state two-hadron interactions drive the CP violation.
L. Heuser, A. Reyes-Torrecilla, C. Hanhart et al.· 3 citations
We present a comprehensive analysis of the angular coefficients of $Z$ and $W$ boson production at hadron colliders in different kinematical ranges, using data from the ATLAS, LHCb, and CMS Collaborations at the LHC, as well as CDF data at the Tevatron. We provide theoretical predictions obtained by consistently combining the resummation of logarithmically enhanced QCD corrections at small transverse momenta $q_T$ up to next-to-next-to-leading logarithmic accuracy (NNLL) with fixed-order calculations at next-to-leading order (NLO), valid at large $q_T$. We quantify the impact of transverse-momentum resummation on the angular coefficients. We find that the inclusion of resummation effects leads to a moderate and systematic improvement in the description of the data in the intermediate $q_T$ region, $q_T \sim 20-50$~GeV, for several angular coefficients, while in the remaining cases it does not degrade the agreement of fixed-order QCD predictions with experimental measurements.
S. Camarda, Giancarlo Ferrera, Lorenzo Rossi et al.· 0 citations
We discuss the factorization of scattering processes near partonic threshold at next-to-leading power (NLP) in the threshold variable $1-z$, with $z \equiv q^2/\hat{s}$. We review the general structure of power-suppressed contributions both in Soft-Collinear Effective Theory (SCET) and in a direct QCD approach, and discuss the definition of NLP jet functions as gauge-invariant operator matrix elements in QCD. As a controlled check of the resulting factorization formula, we verify it explicitly at one and two loops for the massive electromagnetic form factor in the limit $m^2 \ll s$, using the method of regions. We conclude by outlining the two challenges that remain for a systematic resummation of NLP logarithms: the treatment of endpoint divergences in SCET convolutions, and the extension of jet functions to radiative processes capable of describing an arbitrary number of soft-gluon emissions -- the latter being the last missing ingredient for exponentiation, given that the purely soft sector is already understood in terms of generalised webs via the replica trick.
Robin van Bijleveld, J. T. Hoeve, E. Laenen et al.· 0 citations
