Measurements of inclusive jet production are performed in pp and Pb+Pb collisions at sNN=2.76 TeV with the ATLAS detector at the LHC, corresponding to integrated luminosities of 4.0 and 0.14 nb-1, ...respectively. The jets are identified with the anti-kt algorithm with R=0.4, and the spectra are measured over the kinematic range of jet transverse momentum 32<pT<500 GeV and absolute rapidity y<2.1 and as a function of collision centrality. The nuclear modification factor RAA is evaluated, and jets are found to be suppressed by approximately a factor of 2 in central collisions compared to pp collisions. The RAA shows a slight increase with pT and no significant variation with rapidity.
We investigate multilepton signatures, arising from the decays of doubly charged and singly charged Higgs bosons in the Type II seesaw model. Depending on the vacuum expectation value of the triplet ...vΔ, the doubly and singly charged Higgs bosons can decay into a large variety of multilepton final states. We explore all possible decay modes corresponding to different regimes of vΔ that generate distinguishing four and five leptonic signatures. We focus on the 13 TeV Large Hadron Collider (LHC) and further extend the study to a very high energy proton-proton collider (VLHC) with a center-of-mass energy of 100 TeV. We find that a doubly charged Higgs boson of masses around 375 GeV can be discovered at immediate LHC runs. A heavier mass of 630 GeV can instead be discovered at the high-luminosity run of the LHC or at the VLHC with 30 fb−1.
We compute the top quark threshold contributions to the Formula omitted production at the LHC. They appear when the invariant mass of the photon pair, Formula omitted just exceeds two times the mass ...of the top quark and induce some feature in the Formula omitted distribution. We determine the magnitude of this threshold effect and characterize this feature with a simple empirical fitting function to show that it is possible to observe this effect at the LHC in future. We also explore some possible improvements that may enhance its significance.
We observe that four peaks seen in the high energy part of the Ωb spectrum of the recent LHCb experiment are in remarkable agreement with predictions made for molecular Ωb states stemming from the ...meson-baryon interaction, with an approach that applied to the Ωc states gives rise to three states in good agreement with experiment in masses and widths. While the statistical significance of the peaks prevents us from claims of states at the present time, the agreement found should be an incentive to look at this experiment with increased statistics to give an answer to this suggestive idea.
Results from the LHC put severe constraints on models of new physics. This includes constraints on the Higgs sector from the precise measurement of the mass and couplings of the 125 GeV Higgs boson, ...as well as limits from searches for other new particles. We present the procedure to use these constraints in micrOMEGAs by interfacing it to the external codes Lilith, HiggsSignals, HiggsBounds and SModelS. A few dedicated modules are also provided. With these new features, micrOMEGAs_4.3.4 provides a generic framework for evaluating dark matter observables together with collider and non-collider constraints.
Program title: micrOMEGAs4.3
Program Files doi:http://dx.doi.org/10.17632/4ck6jf5vxf.1
Licensing provisions: GNU General Public License 3 (GPL)
Programming language: C and Fortran
Journal reference of previous version: Comput. Phys. Comm. 192 (2015) 322.
Does the new version supersede the previous version?: Yes
Reasons for the new version: The ATLAS and CMS Collaborations at the LHC have performed precision measurements of the Higgs boson as well as numerous searches for new particles. These results impose strong constraints on models of new physics and in particular of dark matter which are complementary to astrophysical and cosmological constraints.
Summary of revisions: This version includes interfaces to codes that fit the Higgs signal strengths, Lilith and HiggsSignals, as well as to HiggsBounds a code that is used to derive limits from searches of new scalar particles and to SModelS that exploits the simplified models results in channels with missing energy. Specific routines to reinterpret the constraints on a new Z’ boson as well as those from monojet searches are added. A routine to automatically extract any vertex from the model file is used to automatically compute the loop-induced di-photon and di-gluon Higgs widths.
Nature of problem: Dark matter models can be severely constrained by precision measurements and searches for new particles at the LHC. Dedicated tools that reinterpret recent LHC results allow for a fast and efficient probe of the parameter space of various dark matter models have been developed. Interfaces to these tools are incorporated in this new version.
Solution method: To use the constraints from the LHC on the Higgs sector and on new particles, mcrOMEGAs is interfaced to the external codes Lilith, HiggsSignal, HiggsBounds and SModelS. A few dedicated modules are also provided. With these new features, micrOMEGAs_4.3 provides a generic framework for evaluating dark matter observables together with collider and non-collider constraints.
We investigate the effect of soft gluon radiations on the azimuthal angle correlation between the total and relative momenta of two jets in inclusive and exclusive dijet processes. We show that the ...final state effect induces a sizable cos(2ϕ) anisotropy due to gluon emissions near the jet cones. The phenomenological consequences of this observation are discussed for various collider experiments, including diffractive processes in ultraperipheral pA and AA collisions, inclusive and diffractive dijet production at the EIC, and inclusive dijet in pp and AA collisions at the LHC.
A measurement is reported of the ratio of branching fractions R(J/ψ)=B(B_{c}^{+}→J/ψτ^{+}ν_{τ})/B(B_{c}^{+}→J/ψμ^{+}ν_{μ}), where the τ^{+} lepton is identified in the decay mode ...τ^{+}→μ^{+}ν_{μ}νover ¯_{τ}. This analysis uses a sample of proton-proton collision data corresponding to 3.0 fb^{-1} of integrated luminosity recorded with the LHCb experiment at center-of-mass energies of 7 and 8 TeV. A signal is found for the decay B_{c}^{+}→J/ψτ^{+}ν_{τ} at a significance of 3 standard deviations corrected for systematic uncertainty, and the ratio of the branching fractions is measured to be R(J/ψ)=0.71±0.17(stat)±0.18(syst). This result lies within 2 standard deviations above the range of central values currently predicted by the standard model.
The LHCb Collaboration at the Large Hadron Collider at CERN discovered two pentaquark states P_{c}(4380) and P_{c}(4450). These two hidden-charm states are interpreted as the loosely bound ...Σ_{c}(2455)D^{*} and Σ_{c}^{*}(2520)D^{*} molecular states in the boson exchange interaction model, which provides an explanation for why the experimental width of P_{c}(4450) is much narrower than that of P_{c}(4380). The discovery of the new resonances P_{c}(4380) and P_{c}(4450), indeed, opens a new page for hadron physics. The partners of P_{c}(4380) and P_{c}(4450) should be pursued in future experiments.
Measurements are made of differential cross-sections of highly boosted pair-produced top quarks as a function of top-quark and tt¯ system kinematic observables using proton-proton collisions at a ...center-of-mass energy of s=13 TeV. The data set corresponds to an integrated luminosity of 36.1 fb−1, recorded in 2015 and 2016 with the ATLAS detector at the CERN Large Hadron Collider. Events with two large-radius jets in the final state, one with transverse momentum pT>500 GeV and a second with pT>350 GeV, are used for the measurement. The top-quark candidates are separated from the multijet background using jet substructure information and association with a b-tagged jet. The measured spectra are corrected for detector effects to a particle-level fiducial phase space and a parton-level limited phase space, and are compared to several Monte Carlo simulations by means of calculated χ2 values. The cross-section for tt¯ production in the fiducial phase-space region is 292±7(stat)±71(syst) fb, to be compared to the theoretical prediction of 384±36 fb.
ForwArd Search ExpeRiment at the LHC Feng, Jonathan L.; Galon, Iftah; Kling, Felix ...
Physical review. D,
2/2018, Volume:
97, Issue:
3
Journal Article
Peer reviewed
Open access
New physics has traditionally been expected in the high-pT region at high-energy collider experiments. If new particles are light and weakly coupled, however, this focus may be completely misguided: ...light particles are typically highly concentrated within a few mrad of the beam line, allowing sensitive searches with small detectors, and even extremely weakly coupled particles may be produced in large numbers there. We propose a new experiment, forward search experiment, or FASER, which would be placed downstream of the ATLAS or CMS interaction point (IP) in the very forward region and operated concurrently there. Two representative on-axis locations are studied: a far location, 400 m from the IP and just off the beam tunnel, and a near location, just 150 m from the IP and right behind the TAN neutral particle absorber. For each location, we examine leading neutrino- and beam-induced backgrounds. As a concrete example of light, weakly coupled particles, we consider dark photons produced through light meson decay and proton bremsstrahlung. We find that even a relatively small and inexpensive cylindrical detector, with a radius of ∼10 cm and length of 5–10 m, depending on the location, can discover dark photons in a large and unprobed region of parameter space with dark photon mass mA′∼10–500 MeV and kinetic mixing parameter ε∼10−6−10−3. FASER will clearly also be sensitive to many other forms of new physics. We conclude with a discussion of topics for further study that will be essential for understanding FASER’s feasibility, optimizing its design, and realizing its discovery potential.
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