Collective behavior has been observed in high-energy heavy-ion collisions for several decades. Collectivity is driven by the high particle multiplicities that are produced in these collisions. At the Large Hadron Collider (LHC), features of collectivity have also been seen in high-multiplicity proton-proton collisions that can attain particle multiplicities comparable to peripheral Pb-Pb collisions. One of the possible signatures of collective behavior is the decrease of femtoscopic radii extracted from pion and kaon pairs emitted from high-multiplicity collisions with increasing pair transverse momentum. This decrease can be described in terms of an approximate transverse mass scaling. In the present work, femtoscopic analyses are carried out by the ALICE collaboration on charged pion and kaon pairs produced in pp collisions at s√=13 TeV from the LHC to study possible collectivity in pp collisions. The event-shape analysis method based on transverse sphericity is used to select for spherical versus jet-like events, and the effects of this selection on the femtoscopic radii for both charged pion and kaon pairs are studied. This is the first time this selection method has been applied to charged kaon pairs. An approximate transverse-mass scaling of the radii is found in all multiplicity ranges studied when the difference in the Lorentz boost for pions and kaons is taken into account. This observation does not support the hypothesis of collective expansion of hot and dense matter that should only occur in high-multiplicity events. A possible alternate explanation of the present results is based on a scenario of common emission conditions for pions and kaons in pp collisions for the multiplicity ranges studied.

The size of the particle emission region in high-energy collisions can be deduced using the femtoscopic correlations of particle pairs at low relative momentum. Such correlations arise due to quantum statistics and Coulomb and strong final state interactions. In this paper, results are presented from femtoscopic analyses of [pi]± [pi]±, K± K±, K$0\atop{S}$K$0\atop{S}$, pp, and $\overline{p}$ $\overline{p}$ correlations from Pb-Pb collisions at sNN=2.76 TeV by the ALICE experiment at the LHC. One-dimensional radii of the system are extracted from correlation functions in terms of the invariant momentum difference of the pair. The comparison of the measured radii with the predictions from a hydrokinetic model is discussed. The pion and kaon source radii display a monotonic decrease with increasing average pair transverse mass mT which is consistent with hydrodynamic model predictions for central collisions. Lastly, the kaon and proton source sizes can be reasonably described by approximate mT scaling.

Femtoscopic correlations with the particle pair combinations K0SK0S and K0SK± are studied in pp collisions at s√=5.02 and 13 TeV by the ALICE experiment. At both energies, boson source parameters are extracted for both pair combinations, by fitting models based on Gaussian size distributions of the sources, to the measured two-particle correlation functions. The interaction model used for the K0SK0S analysis includes quantum statistics and strong final-state interactions through the f0(980) and a0(980) resonances. The model used for the K0SK± analysis includes only the final-state interaction through the a0 resonance. Source parameters extracted in the present work are compared with published values from pp collisions at s√= 7 TeV and the different pair combinations are found to be consistent. From the finding that the strength of the K0SK0S correlations is significantly greater than the strength of the K0SK± correlations, the new results are compatible with the a0 resonance being a tetraquark state of the form (q1,q2 ̄ ̄ ̄ ̄ ̄,s,s ̄ ̄ ̄), where q1 and q2 are u or d quarks.

Preliminary femtoscopic results on identical pions from high statistics data set of Au+Au collisions at {radical}s{sub NN} = 200 GeV taken during the fourth RHIC run are presented. The measured three-dimensional correlation function is studied at low relative momenta using the Gaussian parametrization and the Levy stable parametrization. The latter is expected to better describe the data. As the results show, both parametrizations underestimate the peak of the measured correlation function equally.

Bose-Einstein correlations between identical particles are measured in samples of proton-proton collisions at 0.9 and 7 TeV centre-of-mass energies, recorded by the CMS experiment at the LHC. The signal is observed in the form of an enhancement of number of pairs of same-sign charged particles with small relative momentum. The dependence of this enhancement on kinematic and topological features of the event is studied.

The latest of the 'Lepton Photon' symposium, one of the well-established series of meetings in the high-energy physics community, was successfully organized at the South Campus of Sun Yat-sen University, Guangzhou, China, from August 7-12, 2017, where physicists around the world gathered to discuss the latest advancements in the research field.This proceedings volume of the Lepton Photon 2017 collects contributions by the plenary session speakers and the posters' presenters, which cover the latest results in particle physics, nuclear physics, astrophysics, cosmology, and plans for future facilities.

Two-particle angular correlations were measured in pp collisions at s√=7 TeV for pions, kaons, protons, and lambdas, for all particle/anti-particle combinations in the pair. Data for mesons exhibit an expected peak dominated by effects associated with mini-jets and are well reproduced by general purpose Monte Carlo generators. However, for baryon-baryon and anti-baryon-anti-baryon pairs, where both particles have the same baryon number, a near-side anti-correlation structure is observed instead of a peak. This effect is interpreted in the context of baryon production mechanisms in the fragmentation process. It currently presents a challenge to Monte Carlo models and its origin remains an open question.

We present a systematic study of charged pion and kaon interferometry in Au+Au collisions at √sNN=200 GeV. The kaon mean source radii are found to be larger than pion radii in the outward and longitudinal directions for the same transverse mass; this difference increases for more central collisions. The azimuthal-angle dependence of the radii was measured with respect to the second-order event plane and similar oscillations of the source radii were found for pions and kaons. Hydrodynamic models qualitatively describe the similar oscillations of the mean source radii for pions and kaons, but they do not fully describe the transverse-mass dependence of the oscillations.

Data analysis is in progress for recent experiments performed by the NA44 collaboration with the first running of 160 A GeV 2°8Pb-induced reactions at the CERN SPS. Identified singles spectra were taken for pions, kaons, protons, deuterons, antiprotons and antideuterons. Two-pion interferometry measurements were made for semi-central-triggered 2°8Pb + Pb collisions. An upgraded multi-particle spectrometer allows high statistics data sets of identified particles to be collected near mid-rapidity. A second series of experiments will be performed in the fall of 1995 with more emphasis on identical kaon interferometry and on the measurement of rare particle spectra and correlations. Modest instrumentation upgrades by TAMU are designed to increase the trigger function for better impact parameter selection and improved collection efficiency of valid events. An effort to achieve the highest degree of projectile-target stopping is outlined and it is argued that an excitation function on the SPS is needed to better understand reaction mechanisms. Analysis of experimental results is in the final stages at LBL in the EOS collaboration for two-pion interferometry in the 1.2 A GeV Au+Au reaction, taken with full event characterization. 35 refs., 15 figs., 5 tabs.