Search arXiv⌕ Search
Home/Archive/arXiv

arXiv · 1210.5482

Observation of long-range near-side angular correlations in proton-lead collisions at the LHC

CMS Collaboration
View original source ↗Read source document ↗Export metadata ↓

Abstract

Results on two-particle angular correlations for charged particles emitted in pPb collisions at a nucleon-nucleon center-of-mass energy of 5.02 TeV are presented. The analysis uses two million collisions collected with the CMS detector at the LHC. The correlations are studied over a broad range of pseudorapidity, eta, and full azimuth, phi, as a function of charged particle multiplicity and particle transverse momentum, pt. In high-multiplicity events, a long-range (2 < abs(Delta(eta)) < 4), near-side (Delta(phi) approximately 0) structure emerges in the two-particle Delta(eta)-Delta(phi) correlation functions. This is the first observation of such correlations in proton-nucleus collisions, resembling the ridge-like correlations seen in high-multiplicity pp collisions at sqrt(s) = 7 TeV and in AA collisions over a broad range of center-of-mass energies. The correlation strength exhibits a pronounced maximum in the range of pt = 1-1.5 GeV and an approximately linear increase with charged particle multiplicity for high-multiplicity events. These observations are qualitatively similar to those in pp collisions when selecting the same observed particle multiplicity, while the overall strength of the correlations is significantly larger in pPb collisions.

Explore related subjects

nucl-exhep-ex

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

CMS Collaboration. 2013-03-20. Observation of long-range near-side angular correlations in proton-lead collisions at the LHC. https://doi.org/10.1016/j.physletb.2012.11.025

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related papers

arXiv2026

Jet-like di-hadron correlations in pO, OO, and Ne--Ne collisions

Heavy-ion collisions are primarily studied to investigate the properties of hot and dense nuclear matter, known as the quark--gluon plasma (QGP). However, recent observations of hydrodynamic flow-like behaviour in pp and p--Pb collisions at the LHC suggest the possible formation of QGP droplets even in small collision systems. To bridge the multiplicity gap between small and large systems and to examine the applicability of hydrodynamic descriptions, light-ion collisions were performed for the first time at the LHC in 2025. This contribution presents measurements of the near-side peak width of di-hadron correlations in pO, OO, and Ne--Ne collisions with ALICE, used to search for medium effects. The width of the near-side correlation peak is studied as a function of the average charged-particle multiplicity at midrapidity. At low transverse momentum ($p_{\rm T}$), the near-side peak is broader in OO and Ne--Ne collisions than in pp and pO collisions, and in central collisions its width approaches that measured in Pb--Pb collisions. At higher $p_{\rm T}$ the peak narrows modestly with increasing multiplicity. The results are compared with PYTHIA, AMPT, and JETSCAPE calculations, none of which reproduces the measured widths over the full kinematic range.

nucl-ex↗
arXiv2026

Electromagnetic transition strength in $^{53}$Ca: the lifetime of the $5/2^{-}$ state

High-resolution in-beam $γ$-ray spectroscopy of $^{53}$Ca was performed at the Radioactive Isotope Beam Factory (RIBF) at RIKEN. Excited states in $^{53}$Ca were populated via one-neutron and one-proton removal reactions from a $^{55}$Sc radioactive beam, and the emitted $γ$ rays were detected using the HiCARI hybrid germanium detector array. The lifetime of the first excited $5/2^{-}$ state in $^{53}$Ca was measured for the first time through an analysis of Doppler-roadened $γ$-ray line shapes arising from relativistic recoil velocities. A lifetime of $τ = 11.3_{-11.3}^{+5.3(stat)+3(sys)}$ ps was deduced, corresponding to a reduced transition probability of $B(E2;5/2^{-}{\rightarrow}1/2^{-}) > 2.6 e^{2}fm^{4}$ at the 1$σ$ level, with a best-fit value of $4.5 e^{2}fm^{4}$. The measured transition strength is compared with state-of-the-art shell-model and ab initio calculations, providing a stringent benchmark for shell-model Hamiltonians and effective charges and modern ab initio descriptions of the neutron-rich calcium isotopes approaching the potential $N$ = 40 shell closure.

nucl-ex↗
arXiv2026

Measurements of $γ_v p \to π^+ π^-p'$ Cross Sections with the CLAS12 Detector for $Q^2$ from 2.4-8.0 GeV$^2$ and $W$ from 1.4-2.1 GeV

This paper reports exclusive cross sections for the $ep \to e'π^+π^-p'$ reaction using the CLAS12 detector at Jefferson Laboratory. The extractions of fully integrated and nine single-differential cross sections are presented for the first time for photon virtualities $Q^2$ from 2.4 to 8.0 GeV$^2$ and center-of-mass energies $W$ from 1.4 to 2.1 GeV, which covers a large part of the nucleon resonance region. These data considerably extend the kinematic reach of previous measurements from CLAS that covered $Q^2$ up to 5.0 GeV$^2$. Exclusive $γ_v p \to π^+ π^-p'$ cross section measurements are of particular importance for the extraction of $γ_vpN^*$ resonance electrocouplings across the $N^*$ spectrum, especially in the mass range above 1.6 GeV where several resonances decay preferentially to the $ππN$ final states. The electrocouplings with extended $Q^2$ coverage expected from these new data will enable an improved understanding of the emergence of $N^*$ mass and structure in the transition from the strongly coupled toward the perturbative QCD regime.

nucl-ex↗