118454726
Search for light resonances decaying into pairs of muons as a signal of new physics
A search for groups of collimated muons is performed using a data sample collected by the CMS experiment at the LHC, at a centre-of-mass energy of 7TeV, and corresponding to an integrated luminosity of 35 pb−1. The analysis searches for production of new low-mass states decaying into pairs of muons and is designed to achieve high sensitivity to a broad range of models predicting leptonic jet signatures. With no excess observed over the background expectation, upper limits on the production cross section times branching fraction times acceptance areset, ranging from 0.1 to 0.5 pb at the 95% CL depending on event topology. In addition, the results are interpreted in several benchmark models in the context of supersymmetry with a new light dark sector exploring previously inaccessible parameter space.
37672579
Search for heavy neutrinos and $$\mathrm {W}$$W bosons with right-handed couplings in proton–proton collisions at $$\sqrt{s} = 8\,\text {TeV} $$s=8TeV
A search for heavy, right-handed neutrinos, $$\mathrm {N}_{\ell }$$Nℓ ($$\ell = \mathrm {e}, \mu $$ℓ=e,μ), and right-handed $$\mathrm {W}_{\mathrm {R}}$$WR bosons, which arise in the left-right symmetric extensions of the standard model, has been performed by the CMS experiment. The search was based on a sample of two lepton plus two jet events collected in proton–proton collisions at a center-of-mass energy of 8$$\,\text {TeV}$$TeV corresponding to an integrated luminosity of 19.7 $$\mathrm{fb}^{-1}$$fb-1. For models with strict left-right symmetry, and assuming only one $$\mathrm {N}_{\ell }$$Nℓ flavor contributes significantly to the $$\mathrm {W}_{\mathrm {R}}$$WR decay width, the region in the two-dimensional $$(M_{\mathrm {W}_{\mathrm {R}}}, M_{\mathrm {N}_{\ell }})$$(MWR,MNℓ) mass plane excluded at a 95 % confidence level extends to approximately $$M_{\mathrm {W}_{\mathrm {R}}} = 3.0\,\text {TeV} $$MWR=3.0TeV and covers a large range of neutrino masses below the $$\mathrm {W}_{\mathrm {R}}$$WR boson mass, depending on the value of $$M_{\mathrm {W}_{\mathrm {R}}}$$MWR. This search significantly extends the $$(M_{\mathrm {W}_{\mathrm {R}}}, M_{\mathrm {N}_{\ell }})$$(MWR,MNℓ) exclusion region beyond previous results.
841502
Observation of the diphoton decay of the Higgs boson and measurement of its properties
Observation of the diphoton decay mode of the recently discovered Higgs boson and measurement of some of its properties are reported. The analysis uses the entire dataset collected by the CMS experiment in proton-proton collisions during the 2011 and 2012 LHC running periods. The data samples correspond to integrated luminosities of 5.1$$\,\text {fb}^\text {-1}$$fb-1at $$\sqrt{s}=7\,\text {TeV}\,$$s=7TeV and 19.7$$\,\text {fb}^\text {-1}$$fb-1at 8$$\,\text {TeV}$$TeV . A clear signal is observed in the diphoton channel at a mass close to 125$$\,\text {GeV}$$GeV with a local significance of $$5.7\,\sigma $$5.7σ, where a significance of $$5.2\,\sigma $$5.2σ is expected for the standard model Higgs boson. The mass is measured to be $$124.70\pm 0.34\,\text {GeV} \,=124.70\pm 0.31\,\text {(stat)}\,\pm 0.15\,\text {(syst)}\,\,\text {GeV} \,$$124.70±0.34GeV=124.70±0.31(stat)±0.15(syst)GeV , and the best-fit signal strength relative to the standard model prediction is $$1.14^\mathrm{+0.26}_{-0.23}=1.14\pm 0.21\,\text {(stat)}\,$$1.14-0.23+0.26=1.14±0.21(stat)$$^\mathrm{+0.09}_{-0.05}\,\text {(syst)}\,$$-0.05+0.09(syst)$$^\mathrm{+0.13}_{-0.09}\,\text {(theo)}\,$$-0.09+0.13(theo). Additional measurements include the signal strength modifiers associated with different production mechanisms, and hypothesis tests between spin-0 and spin-2 models.
119204233
Search for new physics in events with same-sign dileptons and b-tagged jets in pp collisions at $ \sqrt {s} = 7 $ TeV
A bstractA search for new physics is performed using isolated same-sign dileptons with at least two b-quark jets in the final state. Results are based on a 4.98 fb−1 sample of proton-proton collisions at a centre-of-mass energy of 7 TeV collected by the CMS detector. No excess above the standard model background is observed. Upper limits at 95% confidence level are set on the number of events from non-standard-model sources. These limits are used to set constraints on a number of new physics models. Information on acceptance and efficiencies are also provided so that the results can be used to confront additional models in an approximate way.
32172622
Measurement of WZ and ZZ production in pp collisions at $$\sqrt{s} = 8\,\text {TeV} $$s=8TeV in final states with b-tagged jets
Measurements are reported of the WZ and ZZ production cross sections in proton-proton collisions at $$\sqrt{s} = 8$$s=8$$\,\text {TeV}$$TeV in final states where one Z boson decays to b-tagged jets. The other gauge boson, either W or Z, is detected through its leptonic decay (either $$\mathrm {W}\rightarrow \mathrm {e}\nu $$W→eν, $$\mathrm {\mu }\nu $$μν or $$\mathrm {Z}\rightarrow \mathrm {e}^+\mathrm {e}^-$$Z→e+e-, $$\mathrm {\mu ^+}\mathrm {\mu ^-}$$μ+μ-, or $${\nu }\overline{\nu }$$νν¯). The results are based on data corresponding to an integrated luminosity of 18.9 fb$$^{-1}$$-1 collected with the CMS detector at the Large Hadron Collider. The measured cross sections, $$\sigma (\mathrm {p}\mathrm {p}\rightarrow \mathrm {W}\mathrm {Z}) = 30.7 \pm 9.3\,\text {(stat.)} \pm 7.1\,\text {(syst.)} \pm 4.1\,\text {(th.)} \pm 1.0\,\text {(lum.)} \,\text {pb} $$σ(pp→WZ)=30.7±9.3(stat.)±7.1(syst.)±4.1(th.)±1.0(lum.)pb and $$\sigma (\mathrm {p}\mathrm {p}\rightarrow \mathrm {Z}\mathrm {Z}) = 6.5 \pm 1.7\,\text {(stat.)} \pm 1.0\,\text {(syst.)} \pm 0.9\,\text {(th.)} \pm 0.2\,\text {(lum.)} \,\text {pb} $$σ(pp→ZZ)=6.5±1.7(stat.)±1.0(syst.)±0.9(th.)±0.2(lum.)pb, are consistent with next-to-leading order quantum chromodynamics calculations.
86624438
Search for massive resonances decaying into pairs of boosted bosons in semi-leptonic final states at s$$ \sqrt{s} $$ = 8 TeV
A bstractA search for new resonances decaying to WW, ZZ, or WZ is presented. Final states are considered in which one of the vector bosons decays leptonically and the other hadronically. Results are based on data corresponding to an integrated luminosity of 19.7 fb−1 recorded in proton-proton collisions at s$$ \sqrt{s} $$ = 8 TeV with the CMS detector at the CERN LHC. Techniques aiming at identifying jet substructures are used to analyze signal events in which the hadronization products from the decay of highly boosted W or Z bosons are contained within a single reconstructed jet. Upper limits on the production of generic WW, ZZ, or WZ resonances are set as a function of the resonance mass and width. We increase the sensitivity of the analysis by statistically combining the results of this search with a complementary study of the all-hadronic final state. Upper limits at 95% confidence level are set on the bulk graviton production cross section in the range from 700 to 10 fb for resonance masses between 600 and 2500 GeV, respectively. These limits on the bulk graviton model are the most stringent to date in the diboson final state.

15715110
Suppressed star formation in circumnuclear regions in seyfert galaxies
Feedback from black hole activity is widely believed to play a key role in regulating star formation and black hole growth. A long-standing issue is the relation between star formation and the fueling of the supermassive black holes in active galactic nuclei (AGNs). We compile a sample of 57 Seyfert galaxies to tackle this issue. We estimate the surface densities of gas and star formation rates in circumnuclear regions (CNRs). Comparing them with the well-known Kennicutt-Schmidt (K-S) law, we find that the star formation rates (SFRs) in the CNRs of most Seyfert galaxies are suppressed in this sample. Feedback is suggested to explain the suppressed SFRs.
16708904
RELATIVISTIC KLYSTRON RESEARCH AT SLAC AND LLNLt
We are developing relativistic klystrons as a power source for high gradient accelerator applications such as large linear electron-positron colliders and compact accelerators. We have attained 200 MW peak power at 11.4 GHz from a relativistic klystron, and 140 MV/m longitudinal gradient in a short 11.4 GHz accelerator section. We report here briefly on our experiments so far. 5 refs., 1 fig., 1 tab.
118998253
Search for rare $B^0_{(s)}\rightarrow \mu^+ \mu^- \mu^+ \mu^-$ decays
A search for the decays $B^0_{s}\rightarrow \mu^+ \mu^- \mu^+ \mu^-$ and $B^0 \rightarrow \mu^+ \mu^- \mu^+ \mu^-$ is performed using data, corresponding to an integrated luminosity of 1.0\ensuremath{\{\,fb}^{-1}}\xspace, collected with the LHCb detector in 2011. The number of candidates observed is consistent with the expected background and, assuming phase-space models of the decays, limits on the branching fractions are set: \{${\ensuremath{\cal B}\xspace}(B^0_{s}\rightarrow \mu^+ \mu^- \mu^+ \mu^-) < 1.6 \ (1.2) \times 10^{-8}$} and \{${\ensuremath{\cal B}\xspace}(B^0 \rightarrow \mu^+ \mu^- \mu^+ \mu^-)< 6.6 \ (5.3) \times 10^{-9}$} at 95\,% (90\,%) confidence level. In addition, limits are set in the context of a supersymmetric model which allows for the $B^0_{(s)}$ meson to decay into a scalar ($S$) and pseudoscalar particle ($P$), where $S$ and $P$ have masses of 2.5 GeV and 214.3 MeV, respectively, both resonances decay into $\mu^+\mu^-$. The branching fraction limits for these decays are \{${\ensuremath{\cal B}\xspace}(\ensuremath{B^0_{s}\rightarrow SP}\xspace) < 1.6 \ (1.2) \times 10^{-8}$} and \{${\ensuremath{\cal B}\xspace}(\ensuremath{B^0\rightarrow SP}\xspace)< 6.3 \ (5.1) \times 10^{-9}$} at 95% (90%) confidence level.
122100793
Search for the $X_b$ and other hidden-beauty states in the $\pi^+ \pi^- \Upsilon(1 \rm S)$ channel at ATLAS
This Letter presents a search for a hidden-beauty counterpart of the X(3872) in the mass ranges of 10.05–10.31 GeV and 10.40–11.00 GeV, in the channel Xb→π+π−ϒ(1S)(→μ+μ−) , using 16.2 fb −1 of s=8 TeV pp collision data collected by the ATLAS detector at the LHC. No evidence for new narrow states is found, and upper limits are set on the product of the Xb cross section and branching fraction, relative to those of the ϒ(2S) , at the 95% confidence level using the CLS approach. These limits range from 0.8% to 4.0%, depending on mass. For masses above 10.1 GeV, the expected upper limits from this analysis are the most restrictive to date. Searches for production of the ϒ(13DJ) , ϒ(10860) , and ϒ(11020) states also reveal no significant signals.
118444783
The QED contribution to $J/\psi$ plus light hadrons production at B-factories
To understand the direct $J/\psi+X_{\mathrm{non-c\bar{c}}}$ production mechanism in $e^{+}e^{-}$ annihilation, in this work, we propose to measure the inclusive $J/\psi$ plus light hadrons (LH) production at B-factories and present a detailed study on its QED production due to $\psi(2S)$ feed-down, where the $\psi(2S)$ are produced in $e^{+}e^{-}\to \psi(2S)+\gamma$ and $e^{+}e^{-}\to \psi(2S)+f\bar{f}, f=lepton,light quark$, and QED contribution to direct $J/\psi+q\bar{q}$ production with $q=u,d,s$ quark. We find that the QED contribution is huge in the whole phase space region, but can be reduced largely and is in the same order as the QCD contribution when a suitable cut on the angel $\theta_{J/\psi}$ between $J/\psi$ and the $e^{+}e^{-}$ beam is made. In this way, the cross section of $J/\psi+LH$ QCD production %which was predicted theoretical at next-to-leading order QCD together with relativistic correction, can be obtained by subtracting the QED contribution from the experimental measurement on inclusive $J/\psi$ plus light hadrons. To help to remove the QED background, we also calculate the angular and momentum distribution of $J/\psi$ in the QED contribution.