374 research outputs found

    The Diboson Excess: Experimental Situation and Classification of Explanations; A Les Houches Pre-Proceeding

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    We examine the `diboson' excess at ∼2\sim 2 TeV seen by the LHC experiments in various channels. We provide a comparison of the excess significances as a function of the mass of the tentative resonance and give the signal cross sections needed to explain the excesses. We also present a survey of available theoretical explanations of the resonance, classified in three main approaches. Beyond that, we discuss methods to verify the anomaly, determining the major properties of the various surpluses and exploring how different models can be discriminated. Finally, we give a tabular summary of the numerous explanations, presenting their main phenomenological features.Comment: 37 pages, 9 Figures, 1 Tabl

    Symmetry Restored in Dibosons at the LHC?

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    A number of LHC resonance search channels display an excess in the invariant mass region of 1.8 - 2.0 TeV. Among them is a 3.4 σ3.4\,\sigma excess in the fully hadronic decay of a pair of Standard Model electroweak gauge bosons, in addition to potential signals in the HWHW and dijet final states. We perform a model-independent cross-section fit to the results of all ATLAS and CMS searches sensitive to these final states. We then interpret these results in the context of the Left-Right Symmetric Model, based on the extended gauge group SU(2)L×SU(2)R×U(1)′SU(2)_L\times SU(2)_R\times U(1)', and show that a heavy right-handed gauge boson WRW_R can naturally explain the current measurements with just a single coupling gR∼0.4g_R \sim 0.4. In addition, we discuss a possible connection to dark matter.Comment: 25 pages, 12 figures, V2: references added, extended discussion of Minimal Left-Right Dark Matter, small correction to decay width - conclusions unchanged, V3: expanded discussion of input parameters and statistical procedure, V4: matches published versio

    Diboson Excesses Demystified in Effective Field Theory Approach

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    We study the collider implication of a neutral resonance which decays to several diboson final states such as W+W−W^+W^-, ZZZZ, and ZγZ\gamma via a minimal set of effective operators. We consider both CP-even and CP-odd bosonic states with spin 0, 1, or 2. The production cross sections for the bosonic resonance states are obtained with the effective operators involving gluons (and quarks), and the branching fractions are obtained with the operators responsible for the interactions with electroweak gauge bosons. We demonstrate that each scenario allows for a broad parameter space which could accommodate the recently-reported intriguing excesses in the ATLAS diboson final states, and discuss how the CP states and spin information of the resonance can be extracted at the LHC run II.Comment: 22 pages, 6 figures, main text slightly modified with results unchange

    Reconciling the 2 TeV Excesses at the LHC in a Linear Seesaw Left-Right Model

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    We interpret the 2 TeV excesses at the LHC in a left-right symmetric model with Higgs doublets and spontaneous DD-parity violation. The light neutrino masses are understood via a linear seesaw, suppressed by a high DD-parity breaking scale, and the heavy neutrinos have a pseudo-Dirac character. In addition, with a suppressed right-handed gauge coupling gR/gL≈0.6g_R / g_L \approx 0.6 in an SO(10)SO(10) embedding, we can thereby interpret the observed eejjeejj excess at CMS. We show that it can be reconciled with the diboson and dijet excesses within a simplified scenario based on our model. Moreover, we find that the mixing between the light and heavy neutrinos can be potentially large which would induce dominant non-standard contributions to neutrinoless double beta decay via long-range λ\lambda and η\eta neutrino exchange.Comment: References added, typos fixed, matches published version, 12 pages, 4 figure

    Interpretations of the ATLAS Diboson Anomaly

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    Recently, the ATLAS Collaboration recorded an interesting anomaly in diboson production with excesses at the diboson invariant mass around 2 TeV in boosted jets of all the WZWZ, W+W−W^+ W^-, and ZZZZ channels. We offer a theoretical interpretation of the anomaly using a phenomenological right-handed model with extra W′W' and Z′Z' bosons. Constraints from narrow total decay widths, dijet cross sections, and W/Z+HW/Z + H production are taken into account. We also comment on a few other possibilities.Comment: v4: match the published version; v3: 18 pages, 6 figures, change to leptophobic Z' model to take into account the EW constraints, and some updates to the analysis and text; v2: 17 pages, 7 figures; a new section and a new figure are added; correct the statement about the WH; references are also adde

    Stealth multiboson signals

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    We introduce the `stealth bosons' SS, light boosted particles with a decay S→AA→qqˉqqˉS \to AA \to q \bar q q \bar q into two daughter bosons AA, which subsequently decay into four quarks that are reconstructed as a single fat jet. Variables that measure the two-pronged structure of fat jets, which are used for diboson resonance searches in hadronic or semi-leptonic final states, classify the jets produced in stealth boson decays as QCD-like - actually, for these variables they may seem more background-like than the QCD background itself. The number of tracks in those jets can also be, on average, much higher than for the fat jets arising from the hadronic decay of boosted WW and ZZ bosons. Therefore, these elusive particles are hard to spot in standard searches. Heavy resonances decaying into two such stealth bosons, or one plus a W/ZW/Z boson, could offer an explanation for the recurrent small excesses found in hadronic diboson resonance searches near an invariant mass of 2 TeV.Comment: LaTeX 32 pages. v2: three appendices added as well as many additional discussions, journal versio
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