Forward neutral pion production in p + p and d + Au collisions at square root sNN=200 GeV

Azimuthal Correlations within Exclusive Dijets with Large Momentum Transfer in Photon-Lead Collisions

The structure of nucleons is multidimensional and depends on the transverse momenta, spatial geometry, and polarization of the constituent partons. Such a structure can be studied using high-energy photons produced in ultraperipheral heavy-ion collisions. The first measurement of the azimuthal angular correlations of exclusively produced events with two jets in photon-lead interactions at large momentum transfer is presented, a process that is considered to be sensitive to the underlying nuclear gluon polarization. This study uses a data sample of ultraperipheral lead-lead collisions at sqrt[s_{NN}]=5.02  TeV, corresponding to an integrated luminosity of 0.38  nb^{-1}, collected with the CMS experiment at the LHC. The measured second harmonic of the correlation between the sum and difference of the two jet transverse momentum vectors is found to be positive, and rising, as the dijet transverse momentum increases. A well-tuned model that has been successful at describing a wide range of proton scattering data from the HERA experiments fails to describe the observed correlations, suggesting the presence of gluon polarization effects.

Evidence for Nonlinear Gluon Effects in QCD and Their Mass Number Dependence at STAR

The STAR Collaboration reports measurements of back-to-back azimuthal correlations of di-π^{0}s produced at forward pseudorapidities (2.6<η<4.0) in p+p, p+Al, and p+Au collisions at a center-of-mass energy of 200 GeV. We observe a clear suppression of the correlated yields of back-to-back π^{0} pairs in p+Al and p+Au collisions compared to the p+p data. The observed suppression of back-to-back pairs as a function of transverse momentum suggests nonlinear gluon dynamics arising at high parton densities. The larger suppression found in p+Au relative to p+Al collisions exhibits a dependence of the saturation scale Q_{s}^{2} on the mass number A. A linear scaling of the suppression with A^{1/3} is observed with a slope of -0.09±0.01.

Pursuing the Precision Study for Color Glass Condensate in Forward Hadron Productions

With the tremendous accomplishments of RHIC and the LHC experiments and the advent of the future electron-ion collider on the horizon, the quest for compelling evidence of the color glass condensate (CGC) has become one of the most aspiring goals in the high energy quantum chromodynamics research. Pursuing this question requires developing the precision test of the CGC formalism. By systematically implementing the threshold resummation, we significantly improve the stability of the next-to-leading-order calculation in CGC for forward rapidity hadron productions in pp and pA collisions, especially in the high p_{T} region, and obtain reliable descriptions of all existing data measured at RHIC and the LHC across all p_{T} regions. Consequently, this technique can pave the way for the precision studies of the CGC next-to-leading-order predictions by confronting them with a large amount of precise data.

VEGFR-2 Inhibitor Apatinib Hinders Endothelial Cells Progression Triggered by Irradiated Gastric Cancer Cells-derived Exosomes

Background: Radiotherapy is a standard treatment for a significant fraction of cancer patients. Nonetheless, to this day radiation resistance is a key impediment in gastric cancer (GC) treatment. Moreover, GC is characterized by its substantial neo-angiogenesis, driven by high levels of vascular endothelial growth factor (VEGF) correlated with the presence of stomach cancer. The aim of our study was to address if VEGFR inhibitors treatments impact the negative effect of radiotherapy regiments of gastric cancer.

Materials and methods: Isolation of exosomes released by SGC-7901 and BGC-823 lines after irradiation at 0 Gy or 6 Gy was performed by differential ultra-centrifugation. Incubation of Human Umbilical Vein Endothelial Cells (HUVEC) was carried out with different concentrations of exosomes from non- or irradiated GC cells to address their proliferation and survival fraction (SF) by MTS. 6 Gy irradiated cells exosomes at concentration of 20 µg/ml were compared to EC incubated with the same exosome concentration from non-irradiated human GC cells over 72-hour time course. Wound-healing and Transwell assays were performed in a migration buffer consisting of exosomes released by non- or irradiated SGC-7901 and BGC-823 cells over 24-hour time course. HUVEC cells stained with DAPI that have passed through a gluten gel were counted in order to monitor their invasion capacity. Employing IC50, 60 µg/ml was determined as the optimal Apatinib (YN968D1) concentration for the half-life of HUVEC, and incubated with exosomes from irradiated GC cells. The aforementioned assays were performed in the background of the same conditions in order to analyse the effect of Apatinib on HUVEC progression.

Results: We show that proliferation, motility and invasive capacity of HUVEC are enhanced upon incubation with exosomes released by irradiated GC cell lines. Importantly, the latter is counteracted by the VEGFR-2 inhibitor Apatinib which hinders ECs progression.

Conclusion / Significance: Combining radiotherapy and VEGFR inhibitors treatment can provide potentially a substantial impact in decreasing cancer death rates by averting the negative effect of radiotherapy regiments and provide better standard for cancer patients.

Towards the test of saturation physics beyond leading logarithm

We present results from the first next-to-leading-order (NLO) numerical analysis of forward hadron production in pA and dA collisions in the small-x saturation formalism. Using parton distributions and fragmentation functions at NLO, as well as the dipole amplitude from the solution to the Balitsky-Kovchegov equation with running coupling, together with the NLO corrections to the hard coefficients, we obtain a good description of the available RHIC data in dAu collisions. In the large p⊥ region beyond the saturation scale, we find that the NLO correction becomes dominant and negative, which indicates that other physics beyond NLO becomes important and should also be taken into account. Furthermore, we make predictions for forward hadron production in pPb collisions at the LHC. This analysis not only incorporates the important NLO corrections for all partonic channels, but also reduces the renormalization scale dependence and helps to significantly reduce the theoretical uncertainties. It therefore provides a precise test of saturation physics beyond the leading logarithmic approximation.

Measurement of the pseudorapidity and centrality dependence of the transverse energy density in Pb-Pb collisions at √(s(NN))=2.76 TeV

The transverse energy (E(T)) in Pb-Pb collisions at 2.76 TeV nucleon-nucleon center-of-mass energy (√(s(NN)) has been measured over a broad range of pseudorapidity (η) and collision centrality by using the CMS detector at the LHC. The transverse energy density per unit pseudorapidity (dE(T)/dη) increases faster with collision energy than the charged particle multiplicity. This implies that the mean energy per particle is increasing with collision energy. At all pseudorapidities, the transverse energy per participating nucleon increases with the centrality of the collision. The ratio of transverse energy per unit pseudorapidity in peripheral to central collisions varies significantly as the pseudorapidity increases from η=0 to |η|=5.0. For the 5% most central collisions, the energy density per unit volume is estimated to be about 14 GeV/fm(3) at a time of 1 fm/c after the collision. This is about 100 times larger than normal nuclear matter density and a factor of 2.6 times higher than the energy density reported at √(s(NN))=200 GeV at the Relativistic Heavy Ion Collider.

Suppression of back-to-back hadron pairs at forward rapidity in d+Au collisions at √s(NN)=200 GeV

Back-to-back hadron pair yields in d+Au and p+p collisions at √s(NN)=200 GeV were measured with the PHENIX detector at the Relativistic Heavy Ion Collider. Rapidity separated hadron pairs were detected with the trigger hadron at pseudorapidity |η|<0.35 and the associated hadron at forward rapidity (deuteron direction, 3.0<η<3.8). Pairs were also detected with both hadrons measured at forward rapidity; in this case, the yield of back-to-back hadron pairs in d+Au collisions with small impact parameters is observed to be suppressed by a factor of 10 relative to p+p collisions. The kinematics of these pairs is expected to probe partons in the Au nucleus with a low fraction x of the nucleon momenta, where the gluon densities rise sharply. The observed suppression as a function of nuclear thickness, p(T), and η points to cold nuclear matter effects arising at high parton densities.

Azimuthal correlations of forward dihadrons in d + Au collisions at RHIC in the color glass condensate

We present a good description of recent experimental data on forward dihadron azimuthal correlations measured in deuteron-gold collisions at the BNL Relativistic Heavy Ion Collider (RHIC), where monojet production has been observed. Our approach is based on the color glass condensate theory for the small-x degrees of freedom of the nuclear wave function, including the use of nonlinear evolution equations with running QCD coupling. Our analysis provides further evidence for the presence of saturation effects in RHIC data.

Forward neutral-pion transverse single-spin asymmetries in p + p collisions at sqrt[s] = 200 GeV

We report precision measurements of the Feynman x (xF) dependence, and first measurements of the transverse momentum (pT) dependence, of transverse single-spin asymmetries for the production of pi0 mesons from polarized proton collisions at sqrt[s] = 200 GeV. The xF dependence of the results is in fair agreement with perturbative QCD model calculations that identify orbital motion of quarks and gluons within the proton as the origin of the spin effects. Results for the pT dependence at fixed xF are not consistent with these same perturbative QCD-based calculations.