Search

We derive simplified expressions for SU(2) Yang-Mills-Higgs monopole solutions presented in the preceding paper.

The color algebra with the outer product ${\mathrm{}[u,v]\mathrm{}}^A=i{f}^{\mathrm{ABC}}(u^B{v}^C+v^C{u}^B)$ is studied for the case of three-quark sources. It is shown to contain two Abelian elements which annihilate the color-singlet state and a sixteen-element ideal which contains an eight-element subalgebra isomorphic to u(2) ⊕ (2). The Jacobi identity is not satisfied on the whole algebra. The quantity that measures the breakdown of the Jacobi identity is calculated.

The results of a search for supersymmetry in events with large missing transverse momentum and heavy-flavor jets using an integrated luminosity corresponding to $2.05{\mathrm{fb}}^{-1}$ of $pp$ collisions at $\sqrt{s}=7\mathrm{TeV}$ recorded with the ATLAS detector at the Large Hadron Collider are reported. No significant excess is observed with respect to the prediction for standard model processes. Results are interpreted in a variety of $R$-parity conserving models in which scalar bottoms and tops are the only scalar quarks to appear in the gluino decay cascade, and in an SO(10) model framework. Gluino masses up to 600–900 GeV are excluded, depending on the model considered.

A generic search for anomalous production of events with at least three charged leptons is presented. The search uses a $pp$-collision data sample at a center-of-mass energy of $\sqrt{s}=7\mathrm{TeV}$ corresponding to $4.6{\mathrm{fb}}^{-1}$ of integrated luminosity collected in 2011 by the ATLAS detector at the CERN Large Hadron Collider. Events are required to contain at least two electrons or muons, while the third lepton may either be an additional electron or muon, or a hadronically decaying tau lepton. Events are categorized by the presence or absence of a reconstructed tau-lepton or $Z$-boson candidate decaying to leptons. No significant excess above backgrounds expected from Standard Model processes is observed. Results are presented as upper limits on event yields from non-Standard-Model processes producing at least three prompt, isolated leptons, given as functions of lower bounds on several kinematic variables. Fiducial efficiencies for model testing are also provided. The use of the results is illustrated by setting upper limits on the production of doubly charged Higgs bosons decaying to same-sign lepton pairs.

Using the data sample of $711{\mathrm{fb}}^{-1}$ of $\mathrm{\Upsilon }(4S)$ on-resonance data taken by the Belle detector at the KEKB asymmetric-energy electron-positron collider, we present the first measurements of branching fractions of the decays $B^{-}\to {\overline{\mathrm{\Lambda }}}_c^{-}{\mathrm{\Xi }}_c^{\prime 0}$, $B^{-}\to {\overline{\mathrm{\Lambda }}}_c^{-}{\mathrm{\Xi }}_c(2645{)}^0$, and $B^{-}\to {\overline{\mathrm{\Lambda }}}_c^{-}{\mathrm{\Xi }}_c(2790{)}^0$. The signal yields for these decays are extracted from the recoil mass spectrum of the system recoiling against ${\overline{\mathrm{\Lambda }}}_c^{-}$ baryons in selected $B^{-}$ candidates. The branching fraction of $B^{-}\to {\overline{\mathrm{\Lambda }}}_c^{-}{\mathrm{\Xi }}_c(2790{)}^0$ is measured to be $(1.1\pm 0.4\pm 0.2)\times {10}^{-3}$, where the first uncertainty is statistical and the second is systematic. The 90% credibility level upper limits on $\mathcal{B}(B^{-}\to {\overline{\mathrm{\Lambda }}}_c^{-}{\mathrm{\Xi }}_c^{\prime 0})$ and $\mathcal{B}(B^{-}\to {\overline{\mathrm{\Lambda }}}_c^{-}{\mathrm{\Xi }}_c(2645{)}^0)$ are determined to be $6.5\times {10}^{-4}$ and $7.9\times {10}^{-4}$, respectively.

A search for supersymmetry involving the pair production of gluinos decaying via third-generation squarks to the lightest neutralino (${\tilde{\chi }}_1^0$) is reported. It uses an LHC proton-proton data set at a center-of-mass energy $\sqrt{s}=13\mathrm{TeV}$ with an integrated luminosity of $3.2{\mathrm{fb}}^{-1}$ collected with the ATLAS detector in 2015. The signal is searched for in events containing several energetic jets, of which at least three must be identified as $b$ jets, large missing transverse momentum, and, potentially, isolated electrons or muons. Large-radius jets with a high mass are also used to identify highly boosted top quarks. No excess is found above the predicted background. For ${\tilde{\chi }}_1^0$ masses below approximately 700 GeV, gluino masses of less than 1.78 TeV and 1.76 TeV are excluded at the 95% C.L. in simplified models of the pair production of gluinos decaying via sbottom and stop, respectively. These results significantly extend the exclusion limits obtained with the $\sqrt{s}=8\mathrm{TeV}$ data set.

Results are presented on the production of jets of particles in association with a $Z/{\gamma }^{*}$ boson, in proton-proton collisions at $\sqrt{s}=7\mathrm{TeV}$ with the ATLAS detector. The analysis includes the full 2010 data set, collected with a low rate of multiple proton-proton collisions in the accelerator, corresponding to an integrated luminosity of $36{\mathrm{pb}}^{-1}$. Inclusive jet cross sections in $Z/{\gamma }^{*}$ events, with $Z/{\gamma }^{*}$ decaying into electron or muon pairs, are measured for jets with transverse momentum $p_T>30\mathrm{GeV}$ and jet rapidity $|y|<4.4$. The measurements are compared to next-to-leading-order perturbative QCD calculations, and to predictions from different Monte Carlo generators implementing leading-order matrix elements supplemented by parton showers.

A search for the standard model Higgs boson produced in association with a vector boson with the decay $H\to \tau \tau$ is presented. The data correspond to $20.3{\mathrm{fb}}^{-1}$ of integrated luminosity from proton-proton collisions at $\sqrt{s}=8\mathrm{TeV}$ recorded by the ATLAS experiment at the LHC during 2012. The data agree with the background expectation, and 95% confidence-level upper limits are placed on the cross section of this process. The observed (expected) limit, expressed in terms of the signal strength $\mu =\sigma /{\sigma }_{\mathrm{SM}}$ for $m_{\mathrm{H}}=125\mathrm{GeV}$, is $\mu <5.6$ (3.7). The measured value of the signal strength is $\mu =2.3\pm 1.6$.

We present measurements of the branching fractions for the singly Cabibbo-suppressed decays $D^{+}\to K^{+}{K}^{-}{\pi }^{+}{\pi }^0$ and $D_s^{+}\to K^{+}{\pi }^{-}{\pi }^{+}{\pi }^0$, and the doubly Cabibbo-suppressed decay $D^{+}\to K^{+}{\pi }^{-}{\pi }^{+}{\pi }^0$, based on $980{\mathrm{fb}}^{-1}$ of data recorded by the Belle experiment at the KEKB $e^{+}{e}^{-}$ collider. We measure these modes relative to the Cabibbo-favored modes $D^{+}\to K^{-}{\pi }^{+}{\pi }^{+}{\pi }^0$ and $D_s^{+}\to K^{+}{K}^{-}{\pi }^{+}{\pi }^0$. Our results for the ratios of branching fractions are $\mathcal{B}(D^{+}\to K^{+}{K}^{-}{\pi }^{+}{\pi }^0)/\mathcal{B}(D^{+}\to K^{-}{\pi }^{+}{\pi }^{+}{\pi }^0)=(11.32\pm 0.13\pm 0.26)\%$, $\mathcal{B}(D^{+}\to K^{+}{\pi }^{-}{\pi }^{+}{\pi }^0)/\mathcal{B}(D^{+}\to K^{-}{\pi }^{+}{\pi }^{+}{\pi }^0)=(1.68\pm 0.11\pm 0.03)\%$, and $\mathcal{B}(D_s^{+}\to K^{+}{\pi }^{-}{\pi }^{+}{\pi }^0)/\mathcal{B}(D_s^{+}\to K^{+}{K}^{-}{\pi }^{+}{\pi }^0)=(17.13\pm 0.62\pm 0.51)\%$, where the uncertainties are statistical and systematic, respectively. The second value corresponds to $(5.83\pm 0.42)\times {\tan }^4{\theta }_C$, where ${\theta }_C$ is the Cabibbo angle; this value is larger than other measured ratios of branching fractions for a doubly Cabibbo-suppressed charm decay to a Cabibbo-favored decay. Multiplying these results by world average values for $\mathcal{B}(D^{+}\to K^{-}{\pi }^{+}{\pi }^{+}{\pi }^0)$ and $\mathcal{B}(D_s^{+}\to K^{+}{K}^{-}{\pi }^{+}{\pi }^0)$ yields $\mathcal{B}(D^{+}\to K^{+}{K}^{-}{\pi }^{+}{\pi }^0)=(7.08\pm 0.08\pm 0.16\pm 0.20)\times {10}^{-3}$, $\mathcal{B}(D^{+}\to K^{+}{\pi }^{-}{\pi }^{+}{\pi }^0)=(1.05\pm 0.07\pm 0.02\pm 0.03)\times {10}^{-3}$, and $\mathcal{B}(D_s^{+}\to K^{+}{\pi }^{-}{\pi }^{+}{\pi }^0)=(9.44\pm 0.34\pm 0.28\pm 0.32)\times {10}^{-3}$, where the third uncertainty is due to the branching fraction of the normalization mode. The first two results are consistent with, but more precise than, the current world averages. The last result is the first measurement of this branching fraction.

A search for dark matter in association with a Higgs boson decaying to two photons is presented. This study is based on data collected with the ATLAS detector, corresponding to an integrated luminosity of $36.1{\mathrm{fb}}^{-1}$ of proton-proton collisions at the LHC at a center-of-mass energy of 13 TeV in 2015 and 2016. No significant excess over the expected background is observed. Upper limits at 95% confidence level are set on the visible cross section for beyond the Standard Model physics processes, and the production cross section times branching fraction of the Standard Model Higgs boson decaying into two photons in association with missing transverse momentum in three different benchmark models. Limits at 95% confidence level are also set on the observed signal in two-dimensional mass planes. Additionally, the results are interpreted in terms of 90% confidence-level limits on the dark-matter–nucleon scattering cross section, as a function of the dark-matter particle mass, for a spin-independent scenario.

We present first evidence that the cosine of the $CP$-violating weak phase $2\beta$ is positive, and hence exclude trigonometric multifold solutions of the Cabibbo-Kobayashi-Maskawa (CKM) Unitarity Triangle using a time-dependent Dalitz plot analysis of $B^0\to D^{(*)}{h}^0$ with $D\to K_S^0{\pi }^{+}{\pi }^{-}$ decays, where $h^0\in \{{\pi }^0,\eta ,\omega \}$ denotes a light unflavored and neutral hadron. The measurement is performed combining the final data sets of the BABAR and Belle experiments collected at the $\mathrm{\Upsilon }(4S)$ resonance at the asymmetric-energy $B$ factories PEP-II at SLAC and KEKB at KEK, respectively. The data samples contain $(471\pm 3)\times {10}^{6}B\overline{B}$ pairs recorded by the BABAR detector and $(772\pm 11)\times {10}^{6}B\overline{B}$ pairs recorded by the Belle detector. The results of the measurement are $\sin 2\beta =0.80\pm 0.14(\mathrm{stat})\pm 0.06(\mathrm{syst})\pm 0.03(\text{model})$ and $\cos 2\beta =0.91\pm 0.22(\mathrm{stat})\pm 0.09(\mathrm{syst})\pm 0.07(\text{model})$. The result for the direct measurement of the angle $\beta$ of the CKM Unitarity Triangle is $\beta =[22.5\pm 4.4(\mathrm{stat})\pm 1.2(\mathrm{syst})\pm 0.6(\text{model})]°$. The measurement assumes no direct $CP$ violation in $B^0\to D^{(*)}{h}^0$ decays. The quoted model uncertainties are due to the composition of the $D^0\to K_S^0{\pi }^{+}{\pi }^{-}$ decay amplitude model, which is newly established by performing a Dalitz plot amplitude analysis using a high-statistics $e^{+}{e}^{-}\to c\overline{c}$ data sample. $CP$ violation is observed in $B^0\to D^{(*)}{h}^0$ decays at the level of 5.1 standard deviations. The significance for $\cos 2\beta >0$ is 3.7 standard deviations. The trigonometric multifold solution $\pi /2-\beta =(68.1\pm 0.7)°$ is excluded at the level of 7.3 standard deviations. The measurement resolves an ambiguity in the determination of the apex of the CKM Unitarity Triangle.

We report on the first measurement of inclusive $J/\psi$ elliptic flow $v_2$ in heavy-ion collisions at the LHC. The measurement is performed with the ALICE detector in Pb-Pb collisions at $\sqrt{s_{NN}}=2.76\mathrm{TeV}$ in the rapidity range $2.5<y<4.0$. The dependence of the $J/\psi$ $v_2$ on the collision centrality and on the $J/\psi$ transverse momentum is studied in the range $0\le p_T<10\mathrm{GeV}/c$. For semicentral Pb-Pb collisions at $\sqrt{s_{NN}}=2.76\mathrm{TeV}$, an indication of nonzero $v_2$ is observed with a largest measured value of $v_2=0.116\pm 0.046(\mathrm{stat})\pm 0.029(\mathrm{syst})$ for $J/\psi$ in the transverse momentum range $2\le p_T<4\mathrm{GeV}/c$. The elliptic flow measurement complements the previously reported ALICE results on the inclusive $J/\psi$ nuclear modification factor and favors the scenario of a significant fraction of $J/\psi$ production from charm quarks in a deconfined partonic phase.

We search for the baryon and lepton number violating charm decays, $D\to p\ell$, where $D$ is either a $D^0$ or a ${\overline{D}}^0$ and $\ell$ is a muon or an electron, using a data sample of $921{\mathrm{fb}}^{-1}$ collected by the Belle detector at the KEKB asymmetric energy $e^{+}{e}^{-}$ collider. In the absence of significant signals, we set upper limits on the branching fractions in the range $(5–8)\times {10}^{-7}$ at a 90% confidence level, depending on the decay mode.

This Letter presents a search for pair production of heavy down-type quarks decaying via $b^{\prime }\to Wt$ in the $\mathrm{\text{lepton}}+\mathrm{\text{jets}}$ channel, as $b^{\prime }{\overline{b}}^{\prime }\to W^{-}t{W}^{+}\overline{t}\to b\overline{b}{W}^{+}{W}^{-}{W}^{+}{W}^{-}\to l^{\pm }\nu b\overline{b}q\overline{q}q\overline{q}q\overline{q}$. In addition to requiring exactly one lepton, large missing transverse momentum, and at least six jets, the invariant mass of nearby jet pairs is used to identify high transverse momentum $W$ bosons. In data corresponding to an integrated luminosity of $1.04{\mathrm{fb}}^{-1}$ from $pp$ collisions at $\sqrt{s}=7\mathrm{TeV}$ recorded with the ATLAS detector, a heavy down-type quark with mass less than 480 GeV can be excluded at the 95% confidence level.

The ATLAS detector is used to search for excited leptons in the electromagnetic radiative decay channel ${\ell }^{*}\to \ell \gamma$. Results are presented based on the analysis of $pp$ collisions at a center-of-mass energy of 7 TeV corresponding to an integrated luminosity of $2.05\mathrm{f}{\mathrm{b}}^{-1}$. No evidence for excited leptons is found, and limits are set on the compositeness scale $\Lambda$ as a function of the excited lepton mass $m_{{\ell }^{*}}$. In the special case where $\Lambda =m_{{\ell }^{*}}$, excited electron and muon masses below 1.87 TeV and 1.75 TeV are excluded at 95% C.L., respectively.

This Letter presents a normalized differential cross-section measurement in a fiducial phase-space region where interference effects between top-quark pair production and associated production of a single top quark with a $W$ boson and a $b$-quark are significant. Events with exactly two leptons ($ee$, $\mu \mu$, or $e\mu$) and two $b$-tagged jets that satisfy a multiparticle invariant mass requirement are selected from $36.1{\mathrm{fb}}^{-1}$ of proton-proton collision data taken at $\sqrt{s}=13\mathrm{TeV}$ with the ATLAS detector at the LHC in 2015 and 2016. The results are compared with predictions from simulations using various strategies for the interference. The standard prescriptions for interference modeling are significantly different from each other but are within $2\sigma$ of the data. State-of-the-art predictions that naturally incorporate interference effects provide the best description of the data in the measured region of phase space most sensitive to these effects. These results provide an important constraint on interference models and will guide future model development and tuning.

We report measurements of the branching fractions of the decays ${\mathrm{\Lambda }}_c^{+}\to {\mathrm{\Sigma }}^{+}{\pi }^{-}{\pi }^{+}$, ${\mathrm{\Lambda }}_c^{+}\to {\mathrm{\Sigma }}^0{\pi }^{+}{\pi }^0$ and ${\mathrm{\Lambda }}_c^{+}\to {\mathrm{\Sigma }}^{+}{\pi }^0{\pi }^0$ relative to the reference channel ${\mathrm{\Lambda }}_c^{+}\to p{K}^{-}{\pi }^{+}$. The analysis is based on the full data sample collected at and near the $\mathrm{\Upsilon }(4S)$ resonance by the Belle detector at the KEKB asymmetric-energy $e^{+}{e}^{-}$ collider, corresponding to an integrated luminosity of $711{\mathrm{fb}}^{-1}$. We measure $\mathcal{B}({\mathrm{\Lambda }}_c^{+}\to {\mathrm{\Sigma }}^{+}{\pi }^{-}{\pi }^{+})/\mathcal{B}({\mathrm{\Lambda }}_c^{+}\to p{K}^{-}{\pi }^{+})=0.719\pm 0.003\pm 0.024$, $\mathcal{B}({\mathrm{\Lambda }}_c^{+}\to {\mathrm{\Sigma }}^0{\pi }^{+}{\pi }^0)/\mathcal{B}({\mathrm{\Lambda }}_c^{+}\to p{K}^{-}{\pi }^{+})=0.575\pm 0.005\pm 0.036$ and $\mathcal{B}({\mathrm{\Lambda }}_c^{+}\to {\mathrm{\Sigma }}^{+}{\pi }^0{\pi }^0)/\mathcal{B}({\mathrm{\Lambda }}_c^{+}\to p{K}^{-}{\pi }^{+})=0.247\pm 0.006\pm 0.019$. The listed uncertainties are statistical and systematic, respectively.

Measurements of four-lepton ($4\ell$, $\ell =e,\mu$) production cross sections at the $Z$ resonance in $pp$ collisions at the LHC with the ATLAS detector are presented. For dilepton and four-lepton invariant mass regions $m_{{\ell }^{+}{\ell }^{-}}>5\mathrm{GeV}$ and $80<m_{4\ell }<100\mathrm{GeV}$, the measured cross sections are $76\pm 18\text{(stat)}\pm 4\text{(syst)}\pm 1.4\text{(lumi)}\mathrm{fb}$ and $107\pm 9\text{(stat)}\pm 4\text{(syst)}\pm 3.0\text{(lumi)}\mathrm{fb}$ at $\sqrt{s}=7$ and 8 TeV, respectively. By subtracting the nonresonant $4\ell$ production contributions and normalizing with $Z\to {\mu }^{+}{\mu }^{-}$ events, the branching fraction for the $Z$ boson decay to $4\ell$ is determined to be $(3.20\pm 0.25\text{(stat)}\pm 0.13\text{(syst)})\times 10^{-6}$, consistent with the standard model prediction.

The ATLAS detector at the Large Hadron Collider is used to search for the lepton flavor violating process $Z\to e\mu$ in $pp$ collisions using $20.3{\mathrm{fb}}^{-1}$ of data collected at $\sqrt{s}=8\mathrm{TeV}$. An enhancement in the $e\mu$ invariant mass spectrum is searched for at the $Z$-boson mass. The number of $Z$ bosons produced in the data sample is estimated using events of similar topology, $Z\to ee$ and $\mu \mu$, significantly reducing the systematic uncertainty in the measurement. There is no evidence of an enhancement at the $Z$-boson mass, resulting in an upper limit on the branching fraction, $\mathcal{B}(Z\to e\mu )<7.5\times 10^{-7}$ at the 95% confidence level.

Azimuthal decorrelations between the two central jets with the largest transverse momenta are sensitive to the dynamics of events with multiple jets. We present a measurement of the normalized differential cross section based on the full data set ($\int \mathcal{L}dt=36{\mathrm{pb}}^{-1}$) acquired by the ATLAS detector during the 2010 $\sqrt{s}=7\mathrm{TeV}$ proton-proton run of the LHC. The measured distributions include jets with transverse momenta up to 1.3 TeV, probing perturbative QCD in a high-energy regime.