Y. Guo

New massive spin-2 particles are predicted in theoretical extensions to the Standard Model (SM) attempting to solve the hierarchy problem. Such theories postulate that gravity is diluted compared to the other fundamental forces because it can propagate in extra spatial dimensions. While such theoretical models are of high experimental interest because they predict massive spin-2 particles ($Y_{2}$) potentially detectable by collider experiments, searches at the Large Hadron Collider (LHC) have thus far produced no significant evidence for their existence. This work considers a hypothetical physics scenario where low coupling strengths between the $Y_{2}$ and quarks/gluons is the underlying reason behind the null $Y_{2}$ search results at the LHC, which have mainly relied on Drell-Yan and gluon-gluon fusion production mechanisms. The focus of this paper is a feasibility study to search for $Y_{2}$ particles using vector boson fusion (VBF) processes at the LHC. In the context of an effective field theory approach with varying couplings $\kappa_{V}$ between $Y_{2}$ and the weak bosons of the SM, we consider the $Y_{2}\to\gamma\gamma$ decay mode to show that the requirement of a diphoton pair combined with two high $p_{T}$ forward jets with large dijet mass and with large separation in pseudorapidity can significantly reduce the SM backgrounds. Assuming proton-proton collisions at $\sqrt{s} = 13$ TeV, we present the total VBF production cross sections, $Y_{2}$ decay widths, and $Y_{2}\to\gamma\gamma$ branching ratios as a function of $m(Y_{2})$, considering universal and non-universal couplings to the SM particles. The unitarity-violating phase space is described. The proposed VBF $Y_{2}\to\gamma\gamma$ search is expected to achieve a discovery reach with signal significance greater than 5$\sigma$ for $Y_{2}$ masses up to 4.4 TeV and $\kappa_{V}$ couplings down to 0.5.

We report the measurement of the leptonic ($e^{+}e^{-}$) decay channel of the $\phi$(1020) meson in Au+Au collisions at $\sqrt{s_{_{NN}}}$ = 200 GeV by the STAR experiment. The transverse momentum ($p_{\rm T}$) spectrum is measured for 0.1 $\le p_{\rm T} \le 2.5$ GeV/$c$ at mid-rapidity ($|y|\le1$). We obtain the $p_{\rm T}$-integrated $\phi$(1020) mass $M_{\phi}=1017.7\pm0.8 (\rm {stat.}) \pm0.9 (\rm {sys.})$ MeV/$c^{2}$ and width $\Gamma_{\phi} = 8.0\pm 2.5(\rm {stat.}) \pm 2.3(\rm {sys.}) \textrm{MeV/}c^{2}$, which are within 1.5\,$\sigma$ and 1.1\,$\sigma$ of the vacuum values, respectively. No significant difference is observed in the measured $p_{\rm T}$ spectrum, $dN/dy$, or $\left $ of the $\phi$(1020) meson between the $e^{+}e^{-}$ and hadronic ($K^{+}K^{-}$) decay channels as measured by the same experiment. The experimental results are compared to a theoretical model including medium-modified $\phi$(1020).

We present strange particle spectra and yields measured atmid-rapidity in sqrt text s=200 GeV proton-proton (p+p) collisions atRHIC. We find that the previously observed universal transverse mass(mathrm mT \equiv\sqrt mathrm p_T 2+\mathrm m2) scaling of hadronproduction in p+p collisions seems to break down at higher \mt and thatthere is a difference in the shape of the \mt spectrum between baryonsand mesons. We observe mid-rapidity anti-baryon to baryon ratios nearunity for Lambda and Xi baryons and no dependence of the ratio ontransverse momentum, indicating that our data do not yet reach thequark-jet dominated region. We show the dependence of the mean transversemomentum (\mpt) on measured charged particle multiplicity and on particlemass and infer that these trends are consistent with gluon-jet dominatedparticle production. The data are compared to previous measurements fromCERN-SPS, ISR and FNAL experiments and to Leading Order (LO) and Next toLeading order (NLO) string fragmentation model predictions. We infer fromthese comparisons that the spectral shapes and particle yields from $p+p$collisions at RHIC energies have large contributions from gluon jetsrather than quark jets.

We present the first measurements of charge-dependent two-particle correlations on momentum-space difference variables {eta}{sub 1}-{eta}{sub 2} (pseudorapidity) and {phi}{sub 1}-{phi}{sub 2} (azimuth) for primary charged hadrons with transverse momentum 0.15 {le} p{sub t} {le} 2 GeV/c and |{eta}| {le} 1.3 from Au-Au collisions at {radical}s{sub NN} = 130 GeV. We observe correlation structures not predicted by theory but consistent with evolution of hadron emission geometry with increasing centrality from one-dimensional fragmentation of color strings to higher-dimensional fragmentation of a hadron-opaque bulk medium.

The cross section for the process e(+)e(-)-> pi(+) pi(-) J/psi is measured precisely at center-of-mass energies from 3.77 to 4.60 GeV using 9 fb(-1) of data collected with the BESIII detector operating at the BEPCII storage ring. Two resonant structures are observed in a fit to the cross section. The first resonance has a mass of (222.0 +/- 3.1 +/- 1.4) MeV/ c(2) and a width of (44.1 +/- 4.3 +/- 2.0)MeV, while the second one has a mass of (4320.0 +/- 10.4 +/- 7.0)MeV/c(2) and a width of (101.4(- 19.7)(+25.3) +/- 10.2) MeV, where the first errors are statistical and second ones are systematic. The first resonance agrees with the Y(4260) resonance reported by previous experiments. The precision of its resonant parameters is improved significantly. The second resonance is observed in e(+)e(-)-> pi(+) pi(-) J/psi for the first time. The statistical significance of this resonance is estimated to be larger than 7.6 sigma. The mass and width of the second resonance agree with the Y(4360) resonance reported by the BABAR and Belle experiments within errors. Finally, the Y(4008) resonance previously observed by the Belle experiment is not confirmed in the description of the BESIII data.

The Born cross sections of $e^{+}e^{-}\to \Sigma^{0}\bar{\Sigma}^{0}$ are measured at center-of-mass energies from $2.3864$ to $3.0200$ GeV using data samples with an integrated luminosity of $328.5$ pb$^{-1}$ collected with the BESIII detector operating at the BEPCII collider. The analysis makes use of a novel reconstruction method for energies near production threshold, while a single-tag method is employed at other center-of-mass energies. The measured cross sections are consistent with earlier results from BaBar, with a substantially improved precision. The cross-section lineshape can be well described by a perturbative QCD-driven energy function. In addition, the effective form factors of the $\Sigma^{0}$ baryon are determined. The results provide precise experimental input for testing various theoretical predictions.