Searches for new physics at the LHC will increasingly depend on
identifying deviations from precision Standard Model predictions. At
the higher energy scales involved for the LHC Run 2, the heavy quarks
play a more prominent role than at the Tevatron. Recent theoretical
developments improve our ability to address multi-scale problems
and properly incorporate heavy quark masses across...
As the LHC begins Run 2 at an even higher energy, one of the top priorities will be to search for new particles (SUSY, …) at the highest energy scales. In addition to direct production of new particles, they can mix with Standard Model (SM) particles to yield discrepancies from the usual predictions. To distinguish this new physics from old uncertainties, we need tools to easily quantify the...
The production of vector bosons (V = W, Z) in association with jets is a stringent test of perturbative QCD and is a background process in searches for new physics. Total and differential cross-section measurements of vector bosons produced in association with jets and heavy flavour quarks in proton-proton collisions performed by the CMS collaboration at the LHC are presented. The measurements...
Drell-Yan W/Z electroweak boson production at the LHC is an essential standard candle which is used for calibration of beam luminosity and detector properties. In addition to proton-proton collisions, the LHC has measured heavy nuclei lead-lead and proton-lead W/Z production. Comparison of these data sets can provide discriminating information of the nuclear modifications present in the Parton...
We present a new scheme for tagging *b*-jets with $p_{T}>500$ GeV, which we call $\mu_{x}$ tagging. At the LHC, the primary method to tag *b*-jets (jets which originate from bottom quarks) relies on tracking their charged constituents. However, when jets are highly boosted, their dense, collimated environment makes precise tracking difficult. Thus, as jet $p_{T}$ approaches 1 TeV, track-based...
The XYZ mesons are unexpected mesons discovered in the last decade that contain a heavy quark and antiquark but have properties that suggest they also have additional constituents. Many of them are surprisingly narrow, and several are definitely tetraquark mesons. Their existence presents a serious challenge to our understanding of the spectrum of QCD. I will explain how the...
Analysis of the 3.0 fb-1 of data collected with the LHCb yielded several important results on exotic hadron candidates including $X(3872)$ and $Z(4430)^+$. The new results will be presented, including the analysis of orbital angular momentum in $X(3872)$ decay to $\pi^+\pi^- J/\psi$ and reanalysis of its quantum numbers.
The exclusive Higgs could be a clean channel to study Higgs properties. The most popular theoretical model for the exclusive Higgs predicts a total cross section of 3 fb at p-p 8 TeV collision energy. This study summarizes a search for the exclusive Higgs boson using ATLAS 8 TeV data, using the channel in which the Higgs decays to a pair of W bosons with different flavor leptons in the final...
DrPeilian, on behalf of the BESIII collaboration LIU(Institute of High Energy Physics Chinese Academy of Sciences, China)
05/08/2015, 17:00
QCD Experiment
The BESIII Experiment at the Beijing Electron Positron Collider (BEPCII) has accumulated the world's largest samples of direct $e^+e^-$ collisions in the tau-charm region. From the collected samples, which include $e^+e^-$ annihilations at J/$\psi$, $\psi$(2S), $\psi$(3770) peaks and in the region from 4 GeV to 4.6 GeV, BESIII has produced many new physics results in the spectroscopy,...
We present a measurement of the production cross section of the D+ mesons in proton-antiproton collisions at 1.96 TeV center-of-mass energy, using the full data set collected by the CDF experiment at the Tevatron collider during Run II. The measurement is performed in a yet unexplored low transverse momentum range, down to 1.5 GeV/c, using events collected with the "zero bias" and "minimum...
We report here the first observation of a direct spin correlation between pairs of like-type and unlike-type $\Lambda$ hyperons produced in inclusive processes at the LHC. The analysis is based on hyperon pairs collected at the ATLAS experiment from pp collisions at a center-of-mass energy of 7 TeV in 2010. A depletion of like-type events when compared to unlike-type events is observed for...
The Proton is a fundamental constituent of matter. In contrast to other fundamental particles like the electron, it is an extended object and has a finite size that can be inferred with some degree of accuracy from several measurements. The electric radius can be extracted from electron-proton scattering experiments,(r_E^p=0.871±0.009 fm) and Lamb shift in Muonic Hydrogen (r_E^p=0.84184±0.0006...
The BABAR Collaboration has an extensive program of studying hadronic cross sections at low-energy e+e- collisions, accessible at the center-of-mass energy of about 10.6 GeV via initial-state radiation. Our measurements allow significant improvements in the precision of the predicted value of the muon anomalous magnetic moment. These improvements are necessary for shedding light on the current...
Inclusive hadron production cross sections and angular distributions in
e+e- collisions shed light on fundamental questions of hadronization and fragmentation processes. We present measurements of the so-called
Collins azimuthal asymmetries in inclusive production of hadron pairs, in the e+e- -> h1 h2 X annihilation process, where the two hadrons (either kaons or pions) are produced in...
In an e+e- B factory charmonium states can be produced through different mechanisms, as in e+e- annihilation, with double charmonium production, and in B-meson decays.
Prompt production of J/psi or psi(2S) in association with a second charmonium state has been observed by both the BaBar and Belle experiments in e+e- annihilation at a center-of-mass energy of 10.58 GeV. These processes...
We perform a new analysis of electron-proton scattering data to determine the proton electric and magnetic radii, enforcing model-independent QCD-based constraints of form factor analyticity. A wide-ranging study of possible systematic effects is performed. An improved analysis is developed that rebins data taken at identical kinematic settings, and avoids a scaling assumption of systematic...
Investigating partonic interactions is one of the primary goals of the PHENIX experiment at the Relativistic Heavy Ion Collider (RHIC). RHIC is specially tailored for studying intrinsic partonic spin-momentum correlations due to its unique ability to collide polarized proton beams. Transverse single-spin asymmetries of order 10% have been measured in PHENIX at center of mass energies from 62.4...
For decades, hadron structure research has progressed toward probing the behavior of constituent quarks and gluons (partons) at smaller and smaller fractions $x$ of their parent hadron's momentum. At sufficiently small $x$, this behavior is expected to transition to saturation, a condition where parton self-interactions and multiple scatterings become significant.
High-energy proton-ion...
sPHENIX is a proposal for a new experiment at RHIC capable of measuring
jets, jet correlations and upsilons to determine the temperature
dependence of transport coefficients of the quark-gluon plasma (QGP).
The sPHENIX detector will acquire a large sample of events with a high
rate data acquisition system from a large acceptance spectrometer with
full hadronic and electromagnetic...
Energy loss of very high energy particles traversing a medium is dominated by the splitting processes of hard bremsstrahlung and pair production. These splitting processes are coherent over large distances, leading to a suppression known as the Landau-Pomeranchuk-Migdal (LPM) effect, relevant to both jet energy loss in quark-gluon plasmas and the evolution of cosmic ray showers. In the QCD...
The study of heavy quark production is an effective way of investigating the properties of the medium created in heavy ion collisions. Heavy quarks are sensitive to the transport properties of the medium since they are produced at the early stages of collision. Heavy quarks can also reveal critical features of the medium because they interact with the medium differently from light quarks....
