Measurement of CP Violation in B0→ ψ (→ l+ l−) KS0 (→ π+ π−) Decays

Journal of Instrumentation

The identification of helium nuclei at LHCb is achieved using a method based on measurements of ionisation losses in the silicon sensors and timing measurements in the Outer Tracker drift tubes. The background from photon conversions is reduced using the RICH detectors and an isolation requirement. The method is developed using ???????? collision data at

arXiv preprint arXiv:2404.19510

The four decays, , are observed for the first time using proton-proton collision data collected with the LHCb detector at a centre-of-mass energy of , corresponding to an integrated luminosity of . By considering the decay as reference channel, the following branching fraction ratios are measured to be, $$\frac{\cal{B} (\Lambda_{b}^{0} \rightarrow \Sigma_{c}^{++} \rm{D}^{-} {K}^{-})}{\cal{B}(\Lambda_{b}^{0} \rightarrow \Lambda_c^{+} \rm \overline{D}^0 {K}^{-})} = {0.282}\pm{0.016}\pm{0.016}\pm{0.005}, \frac{\cal{B}(\Lambda_{b}^{0} \rightarrow \Sigma_{c}^{*++} \rm {D}^{-} {K}^{-})}{\cal{B}(\Lambda_{b}^{0} \rightarrow \Sigma_c^{++} \rm {D}^{-} {K}^{-})} = {0.460}\pm{0.052}\pm{0.028}, \frac{\cal{B}(\Lambda_{b}^{0} \rightarrow \Sigma_{c}^{++} \rm {D}^{*-} {K}^{-})}{\cal{B}(\Lambda_{b}^{0} \rightarrow \Sigma_c^{++} \rm {D}^{-} {K}^{-})} = {2.261}\pm{0.202}\pm{0.129}\pm{0.046}, \frac{\cal{B}(\Lambda_{b}^{0} \rightarrow \Sigma_{c}^{*++} \rm D^{*-} K^{-})}{\cal{B}(\Lambda_{b}^{0} \rightarrow \Sigma_c^{++} \rm D^{-} K^{-})} = {0.896}\pm{0.137}\pm{0.066}\pm{0.018},$$ where the first uncertainties are statistical, the second are systematic, and the third are due to uncertainties in the branching fractions of intermediate particle decays. These initial observations mark the beginning of pentaquark searches in these modes, with more data set to become available following the LHCb upgrade.

Journal of High Energy Physics

A measurement of CP-violating observables in B±→ D* K±and B±→ D* π±decays is made where the photon or neutral pion from the D*→ Dγ or D*→ Dπ 0 decay is not reconstructed. The D meson is reconstructed in the self-conjugate decay modes, D→ π+ π− or D→ K+ K−. The distribution of signal yields in the D decay phase space is analysed in a model-independent way. The measurement uses a data sample collected in proton-proton collisions at centre-of-mass energies of 7, 8, and 13 TeV, corresponding to a total integrated luminosity of approximately 9 fb− 1. The B±→ D* K±and B±→ D* π±CP-violating observables are interpreted in terms of hadronic parameters and the CKM angle γ, resulting in a measurement of γ=(). The total uncertainty includes the statistical and systematic uncertainties, and the uncertainty due to external strong-phase inputs.

Journal of Instrumentation

The identification of helium nuclei at LHCb is achieved using a method based on measurements of ionisation losses in the silicon sensors and timing measurements in the Outer Tracker drift tubes. The background from photon conversions is reduced using the RICH detectors and an isolation requirement. The method is developed using ???????? collision data at

Physical review letters

The decay-time-dependent C P asymmetry in B s 0→ J/ψ (→ μ+ μ−) K+ K− decays is measured using proton-proton collision data, corresponding to an integrated luminosity of 6 fb− 1, collected with the LHCb detector at a center-of-mass energy of 13 TeV. Using a sample of approximately 349 000 B s 0 signal decays with an invariant K+ K− mass in the vicinity of the ϕ (1020) resonance, the C P-violating phase ϕ s is measured, along with the difference in decay widths of the light and heavy mass eigenstates of the B s 0− Bs 0 system, Δ Γ s, and the difference of the average B s 0 and B 0 meson decay widths, Γ s− Γ d. The values obtained are ϕ s=− 0.039±0.022±0.006 rad, Δ Γ s= 0.0845±0.0044±0.0024 ps− 1, and Γ s− Γ d=− 0.05 6− 0.0015+ 0.0013±0.0014 ps− 1, where the first uncertainty is statistical and the second systematic. These are the most precise single measurements to date and are consistent with …

arXiv preprint arXiv:1612.08110

A search for the charmless decay is performed using collision data collected by the LHCb experiment at centre-of-mass energies of and TeV, corresponding to an integrated luminosity of 3 fb. No signal is observed and upper limits on the branching fraction are set to at and at confidence level.

arXiv preprint arXiv:2312.03130

DUNE is an international experiment dedicated to addressing some of the questions at the forefront of particle physics and astrophysics, including the mystifying preponderance of matter over antimatter in the early universe. The dual-site experiment will employ an intense neutrino beam focused on a near and a far detector as it aims to determine the neutrino mass hierarchy and to make high-precision measurements of the PMNS matrix parameters, including the CP-violating phase. It will also stand ready to observe supernova neutrino bursts, and seeks to observe nucleon decay as a signature of a grand unified theory underlying the standard model. The DUNE far detector implements liquid argon time-projection chamber (LArTPC) technology, and combines the many tens-of-kiloton fiducial mass necessary for rare event searches with the sub-centimeter spatial resolution required to image those events with high precision. The addition of a photon detection system enhances physics capabilities for all DUNE physics drivers and opens prospects for further physics explorations. Given its size, the far detector will be implemented as a set of modules, with LArTPC designs that differ from one another as newer technologies arise. In the vertical drift LArTPC design, a horizontal cathode bisects the detector, creating two stacked drift volumes in which ionization charges drift towards anodes at either the top or bottom. The anodes are composed of perforated PCB layers with conductive strips, enabling reconstruction in 3D. Light-trap-style photon detection modules are placed both on the cryostat's side walls and on the central cathode where they are …

Journal of High Energy Physics

The first measurement of the Z boson production cross-section at centre-of-mass energy= 5. 02 TeV in the forward region is reported, using pp collision data collected by the LHCb experiment in year 2017, corresponding to an integrated luminosity of 100±2 pb− 1. The production cross-section is measured for final-state muons in the pseudorapidity range 2. 0< η< 4. 5 with transverse momentum p T> 20 GeV/c. The integrated cross-section is determined to be

JOURNAL OF HIGH ENERGY PHYSICS

Null, N., Aaij, R., Abdelmotteleb, A., Abellan Beteta, C., Abudinén, F., Ackernley, T., et al.(2024). Study of Bc⁺→ χc π⁺ decays. JOURNAL OF HIGH ENERGY PHYSICS, 2024 (2)[10.1007/jhep02 (2024) 173].

European Physical Journal C

Hadrons are systems of quarks bound by the strong interaction, described at the fundamental level by quantum chromodynamics (QCD). The production and decay of hadrons involve the nonperturbative regime of QCD, making calculations challenging. Much progress has been made in recent years in experimental and theoretical studies of beauty mesons, with the aim of testing the Standard Model and

Physical review letters

The decay-time-dependent C P asymmetry in B s 0→ J/ψ (→ μ+ μ−) K+ K− decays is measured using proton-proton collision data, corresponding to an integrated luminosity of 6 fb− 1, collected with the LHCb detector at a center-of-mass energy of 13 TeV. Using a sample of approximately 349 000 B s 0 signal decays with an invariant K+ K− mass in the vicinity of the ϕ (1020) resonance, the C P-violating phase ϕ s is measured, along with the difference in decay widths of the light and heavy mass eigenstates of the B s 0− Bs 0 system, Δ Γ s, and the difference of the average B s 0 and B 0 meson decay widths, Γ s− Γ d. The values obtained are ϕ s=− 0.039±0.022±0.006 rad, Δ Γ s= 0.0845±0.0044±0.0024 ps− 1, and Γ s− Γ d=− 0.05 6− 0.0015+ 0.0013±0.0014 ps− 1, where the first uncertainty is statistical and the second systematic. These are the most precise single measurements to date and are consistent with …

arXiv preprint arXiv:2401.07564

In order to stimulate new engagement and trigger some concrete studies in areas where further work would be beneficial towards fully understanding the physics potential of an Higgs / Top / Electroweak factory, we propose to define a set of focus topics. The general reasoning and the proposed topics are described in this document.

Journal of High Energy Physics

A measurement of CP-violating observables in B±→ D* K±and B±→ D* π±decays is made where the photon or neutral pion from the D*→ Dγ or D*→ Dπ 0 decay is not reconstructed. The D meson is reconstructed in the self-conjugate decay modes, D→ π+ π− or D→ K+ K−. The distribution of signal yields in the D decay phase space is analysed in a model-independent way. The measurement uses a data sample collected in proton-proton collisions at centre-of-mass energies of 7, 8, and 13 TeV, corresponding to a total integrated luminosity of approximately 9 fb− 1. The B±→ D* K±and B±→ D* π±CP-violating observables are interpreted in terms of hadronic parameters and the CKM angle γ, resulting in a measurement of γ=(). The total uncertainty includes the statistical and systematic uncertainties, and the uncertainty due to external strong-phase inputs.

arXiv preprint arXiv:2402.01568

Doping of liquid argon TPCs (LArTPCs) with a small concentration of xenon is a technique for light-shifting and facilitates the detection of the liquid argon scintillation light. In this paper, we present the results of the first doping test ever performed in a kiloton-scale LArTPC. From February to May 2020, we carried out this special run in the single-phase DUNE Far Detector prototype (ProtoDUNE-SP) at CERN, featuring 770 t of total liquid argon mass with 410 t of fiducial mass. The goal of the run was to measure the light and charge response of the detector to the addition of xenon, up to a concentration of 18.8 ppm. The main purpose was to test the possibility for reduction of non-uniformities in light collection, caused by deployment of photon detectors only within the anode planes. Light collection was analysed as a function of the xenon concentration, by using the pre-existing photon detection system (PDS) of ProtoDUNE-SP and an additional smaller set-up installed specifically for this run. In this paper we first summarize our current understanding of the argon-xenon energy transfer process and the impact of the presence of nitrogen in argon with and without xenon dopant. We then describe the key elements of ProtoDUNE-SP and the injection method deployed. Two dedicated photon detectors were able to collect the light produced by xenon and the total light. The ratio of these components was measured to be about 0.65 as 18.8 ppm of xenon were injected. We performed studies of the collection efficiency as a function of the distance between tracks and light detectors, demonstrating enhanced uniformity of response for the anode-mounted PDS …

arXiv preprint arXiv:2402.01336

Measurements of the branching fraction ratio with and decays, denoted and , are presented. The analysis is performed using a dataset corresponding to an integrated luminosity of 5.4 of collision data collected with the LHCb experiment. The branching fractions are normalised with respect to the and decay modes. The combination of the results yields The result is compatible with previous measurements of the branching fractions and predictions based on the Standard Model.

Physical review letters

A measurement of time-dependent C P violation in the decays of B 0 and B 0 mesons to the final states J/ψ (→ μ+ μ−) K S 0, ψ (2 S)(→ μ+ μ−) K S 0 and J/ψ (→ e+ e−) K S 0 with K S 0→ π+ π− is presented. The data correspond to an integrated luminosity of 6 fb− 1 collected at a center-of-mass energy of s= 13 TeV with the LHCb detector. The C P-violation parameters are measured to be S ψ K S 0= 0.717±0.013 (stat)±0.008 (syst) and C ψ K S 0= 0.008±0.012 (stat)±0.003 (syst). This measurement of S ψ K S 0 represents the most precise single measurement of the CKM angle β to date and is more precise than the current world average. In addition, measurements of the C P-violation parameters of the individual channels are reported and a combination with the LHCb Run 1 measurements is performed.

arXiv preprint arXiv:2402.05523

The first observation of the decay is reported with high significance using proton-proton collision data, corresponding to an integrated luminosity of 9fb, collected with the LHCb detector at centre-of-mass energies of 7, 8, and 13 TeV. The ratio of its branching fraction relative to the channel is measured to be $$ \frac{ {\cal{B}}( B_c^+ \to J/\psi \pi^+\pi^0 ) } { {\cal{B}}( B_c^+ \to J/\psi \pi^+ ) } = 2.80 \pm 0.15 \pm 0.11 \pm 0.16 \,, $$ where the first uncertainty is statistical, the second systematic and the third related to imprecise knowledge of the branching fractions for and decays, which are used to determine the detection efficiency. The mass spectrum is found to be consistent with the dominance of an intermediate contribution in accordance with a model based on QCD factorisation.

Journal of High Energy Physics

The production of ψ (2S) mesons in proton-lead collisions at a centre-of-mass energy per nucleon pair of= 8. 16 TeV is studied with the LHCb detector using data corresponding to an integrated luminosity of 34 nb− 1. The prompt and nonprompt ψ (2S) production cross-sections and the ratio of the ψ (2S) to J/ψ cross-section are measured as a function of the meson transverse momentum and rapidity in the nucleon-nucleon centre-of-mass frame, together with forward-to-backward ratios and nuclear modification factors. The production of prompt ψ (2S) is observed to be more suppressed compared to pp collisions than the prompt J/ψ production, while the nonprompt productions have similar suppression factors.

arXiv preprint arXiv:2402.14975

The LHCb collaboration measures production of the exotic hadron (3872) in proton-nucleus collisions for the first time. Comparison with the charmonium state (2) suggests that the exotic (3872) experiences different dynamics in the nuclear medium than conventional hadrons, and comparison with data from proton-proton collisions indicates that the presence of the nucleus may modify (3872) production rates. This is the first measurement of the nuclear modification factor of an exotic hadron.

Physical Review Letters

We demonstrate slow dynamics and constrained motion of domain walls in one-dimensional (1D) interacting bosons with double-well dispersion. In the symmetry-broken regime, the domain-wall motion is “fractonlike”—a single domain wall cannot move freely, while two nearby domain walls can move collectively. Consequently, we find an Ohmic-like linear response and a vanishing superfluid stiffness, which are atypical for a Bose condensate in a 1D translation invariant closed quantum system. Near Lifshitz quantum critical point, we obtain superfluid stiffness ρ s∼ T and sound velocity v s∼ T 1/2, showing similar unconventional low-temperature slow dynamics to the symmetry-broken regime. Particularly, the superfluid stiffness suggests an order by disorder effect as ρ s increases with temperature. Our results pave the way for studying fractons in ultracold atom experiments.

Physical Review Letters

The nuclear charge radius of Si 32 was determined using collinear laser spectroscopy. The experimental result was confronted with ab initio nuclear lattice effective field theory, valence-space in-medium similarity renormalization group, and mean field calculations, highlighting important achievements and challenges of modern many-body methods. The charge radius of Si 32 completes the radii of the mirror pair Ar 32− Si 32, whose difference was correlated to the slope L of the symmetry energy in the nuclear equation of state. Our result suggests L≤ 60 MeV, which agrees with complementary observables.

Physical Review Letters

Current laser-interferometric gravitational wave detectors suffer from a fundamental limit to their precision due to the displacement noise of optical elements contributed by various sources. Several schemes for displacement noise-free interferometers (DFI) have been proposed to mitigate their effects. The idea behind these schemes is similar to decoherence-free subspaces in quantum sensing; ie, certain modes contain information about the gravitational waves but are insensitive to the mirror motion (displacement noise). We derive quantum precision limits for general DFI schemes, including optimal measurement basis and optimal squeezing schemes. We introduce a triangular cavity DFI scheme and apply our general bounds to it. Precision analysis of this scheme with different noise models shows that the DFI property leads to interesting sensitivity profiles and improved precision due to noise mitigation and larger …

Physical Review Letters

The strong coupling of quantum emitters to a cavity mode has been of paramount importance in the development of quantum optics. Recently, also the strong coupling to more than a single mode of an electromagnetic resonator has drawn considerable interest. We investigate how this multimode strong coupling regime can be harnessed to coherently control quantum systems. Specifically, we demonstrate that a Maxwell fish-eye lens can be used to implement a pulsed excitation exchange between two distant quantum emitters. This periodic exchange is mediated by single-photon pulses and can be extended to a photon-exchange between two atomic ensembles, for which the coupling strength is enhanced collectively.

Physical Review Letters

Despite significant theoretical efforts devoted to studying the interaction between quantized light modes and matter, the so-called ultrastrong coupling regime still presents significant challenges for theoretical treatments and prevents the use of many common approximations. Here we demonstrate an approach that can describe the dynamics of hybrid quantum systems in any regime of interaction for an arbitrary electromagnetic (EM) environment. We extend a previous method developed for few-mode quantization of arbitrary systems to the case of ultrastrong light-matter coupling, and show that even such systems can be treated using a Lindblad master equation where decay operators act only on the photonic modes by ensuring that the effective spectral density of the EM environment is sufficiently suppressed at negative frequencies. We demonstrate the validity of our framework and show that it outperforms current …

Physical review letters

The 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.

Physical review letters

This Letter reports the observation of W Z γ production and a measurement of its cross section using 140.1±1.2 fb− 1 of proton-proton collision data recorded at a center-of-mass energy of 13 TeV by the ATLAS detector at the Large Hadron Collider. The W Z γ production cross section, with both the W and Z bosons decaying leptonically, p p→ W Z γ→ ℓ′±ν ℓ+ ℓ− γ (ℓ (′)= e, μ), is measured in a fiducial phase-space region defined such that the leptons and the photon have high transverse momentum and the photon is isolated. The cross section is found to be 2.01±0.30 (stat)±0.16 (syst) fb. The corresponding standard model predicted cross section calculated at next-to-leading order in perturbative quantum chromodynamics and at leading order in the electroweak coupling constant is 1.50±0.06 fb. The observed significance of the W Z γ signal is 6.3 σ, compared with an expected significance of 5.0 σ.

Physical Review Letters

The steady propagation of a (d− 1)-dimensional planer interface in d-dimensional space is studied by analyzing mesoscopic nonconserved order parameter dynamics with two local minima under the influence of thermal noise. In this analysis, an entropic force generating interface propagation is formulated using a perturbation method. It is found that the entropic force singularly depends on an ultraviolet cutoff when d≥ 2. The theoretical calculation is confirmed by numerical simulations with d= 2. The result means that an experimental measurement of the entropic force provides an estimation of the microscopic cutoff of the mesoscopic description.

Physical Review Letters

A search for dark matter in events with a displaced nonresonant muon pair and missing transverse momentum is presented. The analysis is performed using an integrated luminosity of 138 fb− 1 of proton-proton (p p) collision data at a center-of-mass energy of 13 TeV produced by the LHC in 2016–2018. No significant excess over the predicted backgrounds is observed. Upper limits are set on the product of the inelastic dark matter production cross section σ (p p→ A′→ χ 1 χ 2) and the decay branching fraction B (χ 2→ χ 1 μ+ μ−), where A′ is a dark photon and χ 1 and χ 2 are states in the dark sector with near mass degeneracy. This is the first dedicated collider search for inelastic dark matter.

Physical Review Letters

We use explainable neural networks to connect the evolutionary history of dark matter halos with their density profiles. The network captures independent factors of variation in the density profiles within a low-dimensional representation, which we physically interpret using mutual information. Without any prior knowledge of the halos’ evolution, the network recovers the known relation between the early time assembly and the inner profile and discovers that the profile beyond the virial radius is described by a single parameter capturing the most recent mass accretion rate. The results illustrate the potential for machine-assisted scientific discovery in complicated astrophysical datasets.

Physical Review Letters

We develop a generalized field space geometry for higher-derivative scalar field theories, expressing scattering amplitudes in terms of a covariant geometry on the all-order jet bundle. The incorporation of spacetime and field derivative coordinates solves complications due to higher-order derivatives faced by existing approaches to field space geometry. We identify a jet bundle analog to the field space metric that, besides field redefinitions, exhibits invariance under total derivatives. The invariance consequently extends to its amplitude contributions and the canonical covariant geometry.

Physical Review Letters

Quantum computing requires a universal set of gate operations; regarding gates as rotations, any rotation angle must be possible. However a real device may only be capable of B bits of resolution, ie, it might support only 2 B possible variants of a given physical gate. Naive discretization of an algorithm’s gates to the nearest available options causes coherent errors, while decomposing an impermissible gate into several allowed operations increases circuit depth. Conversely, demanding higher B can greatly complexify hardware. Here, we explore an alternative: probabilistic angle interpolation (PAI). This effectively implements any desired, continuously parametrized rotation by randomly choosing one of three discretized gate settings and postprocessing individual circuit outputs. The approach is particularly relevant for near-term applications where one would in any case average over many runs of circuit …

Physical Review Letters

The production of the ψ (2 S) charmonium state was measured with ALICE in Pb-Pb collisions at s NN= 5.02 TeV, in the dimuon decay channel. A significant signal was observed for the first time at LHC energies down to zero transverse momentum, at forward rapidity (2.5< y< 4). The measurement of the ratio of the inclusive production cross sections of the ψ (2 S) and J/ψ resonances is reported as a function of the centrality of the collisions and of transverse momentum, in the region p T< 12 GeV/c. The results are compared with the corresponding measurements in p p collisions, by forming the double ratio [σ ψ (2 S)/σ J/ψ] Pb− Pb/[σ ψ (2 S)/σ J/ψ] p p. It is found that in Pb-Pb collisions the ψ (2 S) is suppressed by a factor of∼ 2 with respect to the J/ψ. The ψ (2 S) nuclear modification factor R AA was also obtained as a function of both centrality and p T. The results show that the ψ (2 S) resonance yield is strongly …

Physical Review Letters

The first measurement of the cross section for incoherent photonuclear production of J/ψ vector mesons as a function of the Mandelstam| t| variable is presented. The measurement was carried out with the ALICE detector at midrapidity,| y|< 0.8, using ultraperipheral collisions of Pb nuclei at a center-of-mass energy per nucleon pair of s NN= 5.02 TeV. This rapidity interval corresponds to a Bjorken-x range (0.3–1.4)× 10− 3. Cross sections are given in five| t| intervals in the range 0.04<| t|< 1 GeV 2 and compared to the predictions by different models. Models that ignore quantum fluctuations of the gluon density in the colliding hadron predict a| t| dependence of the cross section much steeper than in data. The inclusion of such fluctuations in the same models provides a better description of the data.

Physical review letters

This Letter reports the observation of W Z γ production and a measurement of its cross section using 140.1±1.2 fb− 1 of proton-proton collision data recorded at a center-of-mass energy of 13 TeV by the ATLAS detector at the Large Hadron Collider. The W Z γ production cross section, with both the W and Z bosons decaying leptonically, p p→ W Z γ→ ℓ′±ν ℓ+ ℓ− γ (ℓ (′)= e, μ), is measured in a fiducial phase-space region defined such that the leptons and the photon have high transverse momentum and the photon is isolated. The cross section is found to be 2.01±0.30 (stat)±0.16 (syst) fb. The corresponding standard model predicted cross section calculated at next-to-leading order in perturbative quantum chromodynamics and at leading order in the electroweak coupling constant is 1.50±0.06 fb. The observed significance of the W Z γ signal is 6.3 σ, compared with an expected significance of 5.0 σ.

Physical review letters

The 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.

Physical Review Letters

The production of the ψ (2 S) charmonium state was measured with ALICE in Pb-Pb collisions at s NN= 5.02 TeV, in the dimuon decay channel. A significant signal was observed for the first time at LHC energies down to zero transverse momentum, at forward rapidity (2.5< y< 4). The measurement of the ratio of the inclusive production cross sections of the ψ (2 S) and J/ψ resonances is reported as a function of the centrality of the collisions and of transverse momentum, in the region p T< 12 GeV/c. The results are compared with the corresponding measurements in p p collisions, by forming the double ratio [σ ψ (2 S)/σ J/ψ] Pb− Pb/[σ ψ (2 S)/σ J/ψ] p p. It is found that in Pb-Pb collisions the ψ (2 S) is suppressed by a factor of∼ 2 with respect to the J/ψ. The ψ (2 S) nuclear modification factor R AA was also obtained as a function of both centrality and p T. The results show that the ψ (2 S) resonance yield is strongly …

Physical Review Letters

On December 5, 2022, an indirect drive fusion implosion on the National Ignition Facility (NIF) achieved a target gain G target of 1.5. This is the first laboratory demonstration of exceeding “scientific breakeven”(or G target> 1) where 2.05 MJ of 351 nm laser light produced 3.1 MJ of total fusion yield, a result which significantly exceeds the Lawson criterion for fusion ignition as reported in a previous NIF implosion [H. Abu-Shawareb et al.(Indirect Drive ICF Collaboration), Phys. Rev. Lett. 129, 075001 (2022)]. This achievement is the culmination of more than five decades of research and gives proof that laboratory fusion, based on fundamental physics principles, is possible. This Letter reports on the target, laser, design, and experimental advancements that led to this result.

Physical review letters

The 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.

Physical review letters

This Letter reports the observation of W Z γ production and a measurement of its cross section using 140.1±1.2 fb− 1 of proton-proton collision data recorded at a center-of-mass energy of 13 TeV by the ATLAS detector at the Large Hadron Collider. The W Z γ production cross section, with both the W and Z bosons decaying leptonically, p p→ W Z γ→ ℓ′±ν ℓ+ ℓ− γ (ℓ (′)= e, μ), is measured in a fiducial phase-space region defined such that the leptons and the photon have high transverse momentum and the photon is isolated. The cross section is found to be 2.01±0.30 (stat)±0.16 (syst) fb. The corresponding standard model predicted cross section calculated at next-to-leading order in perturbative quantum chromodynamics and at leading order in the electroweak coupling constant is 1.50±0.06 fb. The observed significance of the W Z γ signal is 6.3 σ, compared with an expected significance of 5.0 σ.