6062 research outputs found
Sort by
New Structures in the <math display="inline"><mrow><mi>J</mi><mo>/</mo><mi>ψ</mi><mi>J</mi><mo>/</mo><mi>ψ</mi></mrow></math> Mass Spectrum in Proton-Proton Collisions at <math display="inline"><mrow><msqrt><mrow><mi>s</mi></mrow></msqrt><mo>=</mo><mn>13</mn><mtext> </mtext><mtext> </mtext><mi>TeV</mi></mrow></math>
No full textA search is reported for near-threshold structures in the J/ψJ/ψ invariant mass spectrum produced in proton-proton collisions at s=13 TeV from data collected by the CMS experiment, corresponding to an integrated luminosity of 135 fb-1. Three structures are found, and a model with quantum interference among these structures provides a good description of the data. A new structure is observed with a local significance above 5 standard deviations at a mass of 6638-38+43(stat)-31+16(syst) MeV. Another structure with even higher significance is found at a mass of 6847-28+44(stat)-20+48(syst) MeV, which is consistent with the X(6900) resonance reported by the LHCb experiment and confirmed by the ATLAS experiment. Evidence for another new structure, with a local significance of 4.7 standard deviations, is found at a mass of 7134-25+48(stat)-15+41(syst) MeV. Results are also reported for a model without interference, which does not fit the data as well and shows mass shifts up to 150 MeV relative to the model with interference
Search for an exotic decay of the Higgs boson into a Z boson and a pseudoscalar particle in proton-proton collisions at <math altimg="si1.svg"><msqrt><mrow><mi>s</mi></mrow></msqrt><mo linebreak="goodbreak" linebreakstyle="after">=</mo><mn>13</mn><mrow><mspace width="0.20em"/><mtext>TeV</mtext></mrow></math>
No full textA search for an exotic decay of the Higgs boson to a Z boson and a light pseudoscalar particle (a), decaying to a pair of leptons and a pair of photons, respectively, is presented. The search is based on proton-proton collision data at a center-of-mass energy of s=13TeV, collected with the CMS detector at the LHC and corresponding to an integrated luminosity of 138fb−1. The analysis probes pseudoscalar masses ma between 1 and 30 GeV, leading to two pairs of well-isolated leptons and photons. Upper limits at 95% confidence level are set on the Higgs boson production cross section times its branching fraction to two leptons and two photons. The observed (expected) limits are in the range of 1.1–17.8 (1.7–17.9)fb within the probed ma interval. An excess of data above the expected standard model background with a local (global) significance of 2.6 (1.3) standard deviations is observed for a mass hypothesis of ma=3GeV. Limits on models involving axion-like particles, formulated as an effective field theory, are also reported
A search for rare B → Dμμ decays
No full textA search for rare B → Dμμ decays is performed using proton-proton collision data collected by the LHCb experiment, corresponding to an integrated luminosity of 9 fb. No significant signals are observed in the non-resonant μμ modes, and upper limits of \mathcal{B}\left({B}^0\to {\overline{D}}^0{\mu}^{+}{\mu}^{-}\right)<5.1\times {10}^{-8} , \mathcal{B}\left({B}^{+}\to {D}_s^{+}{\mu}^{+}{\mu}^{-}\right)<3.2\times {10}^{-8} , \mathcal{B}\left({B}_s^0\to {\overline{D}}^0{\mu}^{+}{\mu}^{-}\right)<1.6\times {10}^{-7} and {f}_c/{f}_u\cdotp \mathcal{B}\left({B}_c^{+}\to {D}_s^{+}{\mu}^{+}{\mu}^{-}\right)<9.6\times {10}^{-8} are set at the 95 % confidence level, where f and f are the fragmentation fractions of a B meson with a c and u quark respectively in proton-proton collisions. Each result is either the first such measurement or an improvement by three orders of magnitude on an existing limit. Separate upper limits are calculated when the muon pair originates from a J/ψ → μμ decay. The branching fraction of multiplied by the fragmentation-fraction ratio is measured to bewhere the first uncertainty is statistical and the second systematic.[graphic not available: see fulltext
Evidence for the Higgs Boson Decay to a <math display="inline"><mi>Z</mi></math> Boson and a Photon at the LHC
No full textThe first evidence for the Higgs boson decay to a Z boson and a photon is presented, with a statistical significance of 3.4 standard deviations. The result is derived from a combined analysis of the searches performed by the ATLAS and CMS Collaborations with proton-proton collision datasets collected at the CERN Large Hadron Collider (LHC) from 2015 to 2018. These correspond to integrated luminosities of around 140 fb-1 for each experiment, at a center-of-mass energy of 13 TeV. The measured signal yield is 2.2±0.7 times the standard model prediction, and agrees with the theoretical expectation within 1.9 standard deviations
Far-from-equilibrium attractors with full relativistic Boltzmann approach in boost-invariant and non-boost-invariant systems
No full textWe study the universal behavior associated with a Relativistic Boltzmann Transport (RBT) approach with the full collision integral in 0+1D conformal systems. We show that all momentum moments of the distribution function exhibit universal behavior. Furthermore, the RBT approach allows to calculate the full distribution function, showing that an attractor behavior is present in both the longitudinal and transverse momentum dependence. We compare our results to the far-from-equilibrium attractors determined with other approaches, such as kinetic theory in Relaxation Time Approximation (RTA) and relativistic hydrodynamic theories, both in their viscous (DNMR) an anisotropic (aHydro) formulations, finding a very similar evolution, but an even faster thermalization in RBT for higher order moments. For the first time, we extended this analysis also to study the attractor behavior under a temperature-dependent viscosity , accounting also for the rapid increase toward the hadronic phase. We find that a partial breaking of the scaling behavior with respect to emerges only at generating a transient deviation from attractors; interestingly this in realistic finite systems may occur around the freeze-out dynamics. Finally, we investigate for the first time results beyond the boost-invariant picture, finding that also in such a case the system evolves toward the universal attractor. In particular, we present the forward and pull-back attractors at different space-time rapidities including rapidity regions where initially the distribution function is even vanishing
Observation of <math display="inline"><msubsup><mi>D</mi><mi>s</mi><mo>+</mo></msubsup><mo stretchy="false">→</mo><msup><mi>η</mi><mo>′</mo></msup><msup><mi>μ</mi><mo>+</mo></msup><msub><mi>ν</mi><mi>μ</mi></msub></math>, Precision Test of Lepton Flavor Universality with <math display="inline"><msubsup><mi>D</mi><mi>s</mi><mo>+</mo></msubsup><mo stretchy="false">→</mo><msup><mi>η</mi><mrow><mo stretchy="false">(</mo><mo>′</mo><mo stretchy="false">)</mo></mrow></msup><msup><mi>l</mi><mo>+</mo></msup><msub><mi>ν</mi><mi>l</mi></msub></math>, and First Measurements of <math display="inline"><msubsup><mi>D</mi><mi>s</mi><mo>+</mo></msubsup><mo stretchy="false">→</mo><msup><mi>η</mi><mrow><mo stretchy="false">(</mo><mo>′</mo><mo stretchy="false">)</mo></mrow></msup><msup><mi>μ</mi><mo>+</mo></msup><msub><mi>ν</mi><mi>μ</mi></msub></math> Decay Dynamics
No full textBy analyzing 7.33 fb-1 of e+e- annihilation data collected at center-of-mass energies between 4.128 and 4.226 GeV with the BESIII detector, we report the observation of the semileptonic decay Ds+→η′μ+νμ, with a statistical significance larger than 10σ, and the measurements of the Ds+→ημ+νμ and Ds+→η′μ+νμ decay dynamics for the first time. The branching fractions of Ds+→ημ+νμ and Ds+→η′μ+νμ are determined to be (2.235±0.051stat±0.052syst)% and (0.801±0.055stat±0.028syst)%, respectively, with precision improved by factors of 6.0 and 6.6 compared to the previous best measurements. Combined with the results for the decays Ds+→ηe+νe and Ds+→η′e+νe, the ratios of the decay widths are examined both inclusively and in several ℓ+νℓ four-momentum transfer ranges. No evidence for lepton flavor universality violation is found within the current statistics. The products of the hadronic form factors f+,0η(′)(0) and the c→s Cabibbo-Kobayashi-Maskawa matrix element |Vcs| are determined. The results based on the two-parameter series expansion are f+,0η(0)|Vcs|=0.452±0.010stat±0.007syst and f+,0η′(0)|Vcs|=0.504±0.037stat±0.012syst, which help to constrain present models on f+,0η(′)(0). The forward-backward asymmetries are determined to be ⟨AFBη⟩=-0.059±0.031stat±0.005syst and ⟨AFBη′⟩=-0.064±0.079stat±0.006syst for the first time, which are consistent with the theoretical calculation
Study of decays at = 8 TeV with the ATLAS detector
No full textThis paper presents a study of decays with the ATLAS detector at the Large Hadron Collider. The analysis uses a proton–proton data sample corresponding to an integrated luminosity of 20.2 fb collected at a centre-of-mass energy = 8 TeV. Integrated fiducial cross-sections together with normalised differential fiducial cross-sections, sensitive to the kinematics of final-state QED radiation, are obtained. The results are found to be in agreement with state-of-the-art predictions for final-state QED radiation. First measurements of decays are also reported
Magic in generalized Rokhsar-Kivelson wavefunctions
No full textMagic is a property of a quantum state that characterizes its deviation from a stabilizer state, serving as a useful resource for achieving universal quantum computation e.g., within schemes that use Clifford operations. In this work, we study magic, as quantified by the stabilizer Renyi entropy, in a class of models known as generalized Rokhsar-Kivelson systems, i.e., Hamiltonians that allow a stochastic matrix form (SMF) decomposition. The ground state wavefunctions of these systems can be written explicitly throughout their phase diagram, and their properties can be related to associated classical statistical mechanics problems, thereby allowing powerful analytical and numerical approaches that are not usually available in conventional quantum many body settings. As a result, we are able to express the SRE in terms of wave function coefficients that can be understood as a free energy difference of related classical problems. We apply this insight to a range of quantum many body SMF Hamiltonians, which affords us to study numerically the SRE of large high-dimensional systems, and in some cases to obtain analytical results. We observe that the behaviour of the SRE is relatively featureless across quantum phase transitions in these systems, although it is indeed singular (in its first or higher order derivative, depending on the nature of the transition). On the contrary, we find that the maximum of the SRE generically occurs at a cusp away from the quantum critical point, where the derivative suddenly changes sign. Furthermore, we compare the SRE and the logarithm of overlaps with specific stabilizer states, asymptotically realised in the ground state phase diagrams of these systems. We find that they display strikingly similar behaviors, which in turn establish rigorous bounds on the min-relative entropy of magic
Heavy-flavor transport and hadronization in <math display="inline"><mrow><mi>p</mi><mi>p</mi></mrow></math> collisions
No full textRecent experimental results on the Λc+/D0 ratio in proton-proton (pp) collisions have revealed a significant enhancement compared to expectations based on universal fragmentation fractions/functions across different colliding systems, from e+e- to pp. This unexpected enhancement has sparked speculation about the potential effects of a deconfined medium impacting hadronization, previously considered exclusive to heavy-ion collisions. In this study, we propose a novel approach that assumes the formation of a small, deconfined, and expanding fireball even in pp collisions, where charm quarks can undergo rescattering and hadronization. We make use of the same in-medium hadronization mechanism developed for heavy-ion collisions, which involves local color-neutralization through recombination of charm quarks with nearby opposite color charges from the background fireball. Our model incorporates the presence of diquark excitations in the hot medium, which promotes the formation of charmed baryons. Moreover, the recombination process, involving closely aligned partons from the same fluid cell, effectively transfers the collective flow of the system to the final charmed hadrons. We show that this framework can qualitatively reproduce the observed experimental findings in heavy-flavor particle-yield ratios, pT-spectra and elliptic-flow coefficients. Our results provide new, complementary supporting evidence that the collective phenomena observed in small systems naturally have the same origin as those observed in heavy-ion collisions
Search for gravitational-wave bursts in LIGO data at the Schenberg antenna sensitivity range
No full textThe Brazilian Mario Schenberg gravitational-wave detector was initially designed in the early 2000s and remained operational until 2016 when it was disassembled. To assess the feasibility of reassembling the Schenberg antenna, its capability to detect gravitational waves (GW) within its designed sensitivity parameters needs to be evaluated. Detection of significant signals would serve as a catalyst for rebuilding the detector. Although the antenna is currently disassembled, insights can be gleaned from the third observing run (O3) data of the LIGO detectors, given the similarities between Schenberg's ultimate sensitivity and the interferometers' sensitivity in the [3150–3260] Hz band. The search focused on signals lasting from milliseconds to seconds, with no assumptions about their morphology, polarization, and arrival sky direction. Data analysis was performed using the coherent WaveBurst pipeline in the frequency range between 512 Hz and 4096 Hz, specifically targeting signals with bandwidths overlapping the Schenberg frequency band. However, the O3 data did not yield statistically significant evidence of GW bursts. This null result allowed for the characterization of the search efficiency in identifying simulated signal morphologies and setting upper limits on the GW burst event rate as a function of strain amplitude. The current search, and by extension the advanced version of the Schenberg antenna (aSchenberg), can detect sources emitting isotropically 5×10-6M⊙c2 in GWs from a distance of 10 kiloparsecs with a 50% detection efficiency at a false alarm rate of 1 per 100 years. Moreover, we revisited estimations of detecting f modes of neutron stars excited by glitches, setting the upper limit of the f-mode energy for the population of Galactic pulsars to ∼8×10-8M⊙c2 at 3205 Hz. Our simulations and the defined detection criteria suggest f modes are a very unlikely source of gravitational waves for the aSchenberg. Nevertheless, its potential in probing other types of gravitational wave short transients, such as those arising from supernova explosions, giant flares from magnetars, postmerger phase of binary neutron stars, or the inspiral of binaries of primordial black holes with subsolar masses, remains promising