We present a determination of the Cabibbo-Kobayashi-Maskawa matrix element $|V_{cb}|$ from the decay $B\to D\ellν_\ell$ using a $365~\mathrm{fb}^{-1}$$e^+e^-\toΥ(4S)\to B\bar B$ data sample recorded by the Belle II experiment at the SuperKEKB collider. The semileptonic decay of one $B$ meson is reconstructed in the modes $B^0\to D^-(\to K^+π^-π^-)\ell^+ν_\ell$ and $B^+\to \bar D^0(\to K^+π^-)\ell^+ν_\ell$, where $\ell$ denotes either an electron or a muon. Charge conjugation is implied. The second $B$ meson in the $Υ(4S)$ event is not reconstructed explicitly. Using an inclusive reconstruction of the unobserved neutrino momentum, we determine the recoil variable $w=v_B\cdot v_D$, where $v_B$ and $v_D$ are the 4-velocities of the $B$ and $D$ mesons. We measure the total decay branching fractions to be $\mathcal{B}(B^0\to D^-\ell^+ν_\ell)=(2.06 \pm 0.05\,(\mathrm{stat.}) \pm 0.10\,(\mathrm{sys.}))\%$ and $\mathcal{B}(B^+\to\bar D^0\ell^+ν_\ell)=(2.31 \pm 0.04\,(\mathrm{stat.}) \pm 0.09\,(\mathrm{sys.}))\%$. We probe lepton flavor universality by measuring $\mathcal{B}(B\to Deν_e)/\mathcal{B}(B\to Dμν_μ)=1.020 \pm 0.020\,(\mathrm{stat.})\pm 0.022\,(\mathrm{sys.})$. Fitting the partial decay branching fraction as a function of $w$ and using the average of lattice QCD calculations of the $B\to D$ form factor, we obtain $ |V_{cb}|=(39.2\pm 0.4\,(\mathrm{stat.}) \pm 0.6\,(\mathrm{sys.}) \pm 0.5\,(\mathrm{th.})) \times 10^{-3}$.
Differential decay rate $d\Gamma/dw$ for $B \to D \ell \nu$ averaged over 4 modes. The uncertainty listed represents the total uncertainty from statistical and systematic sources.
Differential decay rates $d\Gamma/dw$ for individual $B \to D \ell \nu$ modes. The uncertainty listed represents the total uncertainty from statistical and systematic sources.
Correlations (stat.+syst.) between the $d\Gamma_i/dw$ bins for the averaged $B \rightarrow D \ell \nu$ spectrum (10x10). Element indices 0-9 correspond to $w$ bins: 0: [1.00, 1.06], 1: [1.06, 1.12], 2: [1.12, 1.18], 3: [1.18, 1.24], 4: [1.24, 1.30], 5: [1.30, 1.36], 6: [1.36, 1.42], 7: [1.42, 1.48], 8: [1.48, 1.54], 9: [1.54, 1.59]
The vacuum is now understood to possess a rich and complex structure, characterized by fluctuating energy fields and a condensate of virtual quark-antiquark pairs. The spontaneous breaking of the approximate chiral symmetry, signaled by the nonvanishing quark condensate $\langle q\bar{q}\rangle$, is dynamically generated through topologically nontrivial gauge configurations such as instantons. The precise mechanism linking the chiral symmetry breaking to the mass generation associated with quark confinement remains a profound open question in Quantum Chromodynamics (QCD) - the fundamental theory of strong interaction. High energy proton-proton collisions could liberate virtual quark-antiquark pairs from the vacuum that subsequently undergo confinement to form hadrons, whose properties could serve as probes into QCD confinement and the quark condensate. Here, we report evidence of spin correlations in $Λ\barΛ$ hyperon pairs inherited from spin-correlated strange quark-antiquark virtual pairs. Measurements by the STAR experiment at the Relativistic Heavy-Ion Collider (RHIC) at Brookhaven National Laboratory reveal a relative polarization signal of $(18 \pm 4)\%$ that links the virtual spin-correlated quark pairs from the QCD vacuum to their final-state hadron counterparts. Crucially, this correlation vanishes when the hyperon pairs are widely separated in angle, consistent with the decoherence of the quantum system. Our findings provide a new experimental paradigm for exploring the dynamics and interplay of quark confinement and entanglement.
$\mathrm{d}N/\mathrm{d}\cos\theta^\star$ distributions of decay (anti-)protons for short-range pairs ($|\Delta y| < 0.5$ and $|\Delta \phi| < \pi/3$) $\Lambda\bar{\Lambda}$, $\Lambda\Lambda$, and $\bar{\Lambda}\bar{\Lambda}$ hyperon pairs measured at mid-rapidity ($|y| < 1$).
$\mathrm{d}N/\mathrm{d}\cos\theta^\star$ distributions of decay (anti-)protons for long-range pairs ($0.5 < |\Delta y| < 2.0$ or $\pi/3 <|\Delta \phi| < \pi$) $\Lambda\bar{\Lambda}$, $\Lambda\Lambda$, and $\bar{\Lambda}\bar{\Lambda}$ hyperon pairs measured at mid-rapidity ($|y| < 1$).
Spin correlation $P_\mathrm{\Lambda_1\Lambda_2}$ of short-range $\Lambda\bar{\Lambda}$ (1), $\Lambda\Lambda$ (2), and $\bar{\Lambda}\bar{\Lambda}$ (3) hyperon pars and $K^0_\mathrm{S}K^0_\mathrm{S}$ (4) meson pairs.
We present the results of a search for the charged-lepton-flavor violating decays $B^0 \rightarrow K^{*0}\tau^\pm \ell^{\mp}$, where $\ell^{\mp}$ is either an electron or a muon. The results are based on 365 fb$^{-1}$ and 711 fb$^{-1}$ datasets collected with the Belle II and Belle detectors, respectively. We use an exclusive hadronic $B$-tagging technique, and search for a signal decay in the system recoiling against a fully reconstructed $B$ meson. We find no evidence for $B^0 \rightarrow K^{*0}\tau^\pm \ell^{\mp}$ decays and set upper limits on the branching fractions in the range of $(2.9-6.4)\times10^{-5}$ at 90% confidence level.
$M_{\tau}$ distribution in signal region, (OS$e$, Belle)
$M_{\tau}$ distribution in signal region, (OS$e$, Belle II)
$M_{\tau}$ distribution in signal region, (OS$\mu$, Belle)
The STAR Collaboration reports measurements of acoplanarity using semi--inclusive distributions of charged--particle jets recoiling from direct photon and $π^{0}$ triggers, in central Au+Au and $pp$ collisions at $\sqrt{s_\mathrm{NN}}=200$ GeV. Significant medium--induced acoplanarity broadening is observed for large but not small recoil jet resolution parameter, corresponding to recoil jet yield enhancement up to a factor of $\approx20$ for trigger--recoil azimuthal separation far from $π$. This phenomenology is indicative of the response of the Quark--Gluon Plasma to excitation, but not the scattering of jets off of its quasiparticles. The measurements are not well--described by current theoretical models which incorporate jet quenching.
Corrected Yield R=0.2 pi0+jet 10-15 pp at sqrt{s_{NN}}=200 GeV
Corrected Yield R=0.2 pi0+jet 15-20 pp at sqrt{s_{NN}}=200 GeV
Corrected Yield R=0.5 pi0+jet 10-15 pp at sqrt{s_{NN}}=200 GeV
The polarization of Lambda, Anti-Lambda, Xi, and Anti-Xi hyperons along the angular momentum of the system has been measured in isobar collisions of Ru+Ru and Zr+Zr at $\sqrt{s_{NN}}$ = 200 GeV with the STAR detector at RHIC. The polarization dependence on collision centrality is explored and found to show an increasing trend in more peripheral collisions. Dependencies on transverse momentum and pseudorapidity are investigated for Lambda and Anti-Lambda hyperons, but no significant dependence has been observed. The polarization measurements for Lambda and Anti-Lambda are consistent with each other, indicating little contribution of the spin-magnetic coupling in the observed polarization. The results for Lambda hyperons measurements are qualitatively consistent with hydrodynamic calculations incorporating effects from shear-induced polarization and thermal vorticity, and show no obvious system size dependence in comparison with previous results in Au+Au collisions. For the first time, the dependence of the polarization on the hyperon's emission azimuthal angle with respect to the second harmonic event plane is extracted and shows stronger polarization for the in-plane emitted hyperons at the level of 2.4$\sigma$ significance in 20-50% centrality. The measurements of Xi hyperons polarization via the polarization transfer analysis exhibit a finite positive polarization, 2.9$\sigma$ significance in 20-50% centrality, slightly enhanced compared to the inclusive Lambda polarization.
Resolutions of the first-order event plane from the ZDC-SMDs as a function of collision centrality in Ru+Ru and Zr+Zr collisions at $\sqrt{s_{NN}}$ = 200 GeV.
Resolutions of the second-order event plane from the TPC as a function of collision centrality in Ru+Ru and Zr+Zr collisions at $\sqrt{s_{NN}}$ = 200 GeV.
Global polarization of $\Lambda$ and $\bar\Lambda$ and their difference as a function of centrality in combined Ru+Ru and Zr+Zr collisions at $\sqrt{s_{NN}}$ = 200 GeV.
We present a search for the rare flavor-changing neutral-current decay $B^0 \to K^{\ast 0} τ^+ τ^-$ with data collected by the Belle II experiment at the SuperKEKB electron-positron collider. The analysis uses a 365 fb$^{-1}$ data sample recorded at the center-of-mass energy of the $Υ(4S)$ resonance. One of the $B$ mesons produced in the $Υ(4S)\to B^0 \bar{B}^0$ process is fully reconstructed in a hadronic decay mode, while its companion $B$ meson is required to decay into a $K^{\ast 0}$ and two $τ$ leptons of opposite charge. The $τ$ leptons are reconstructed in final states with a single electron, muon, charged pion or charged $ρ$ meson, and additional neutrinos. We set an upper limit on the branching ratio of $BR(B^0 \to K^{\ast 0} τ^+ τ^-) < 1.8 \times 10^{-3}$ at the 90% confidence level, which is the most stringent constraint reported to date.
- - - - - - - - Overview of HEPData Record - - - - - - - -<br/><br/></ul><b>Post-fit yields:</b><ul><li><a href="159541?version=1&table=Postfit%20yields:%20fit%20variable">Fit variable $\eta(\rm{BDT})$</a></ul><b>Signal $q^{2}$:</b><ul><li><a href="159541?version=1&table=Generated%20$q^2$"> Generated $q^{2}$ distribution </a></ul><b>Signal selection efficiency:</b><ul><li><a href="159541?version=1&table=Selection%20efficiency"> Selection efficieny in signal region </a>
Observed yields and fit results in bins of $\eta(\rm{BDT})$ as obtained by the fit on the four signal categories, corresponding to an integrated luminosity of 365 fb$^{-1}$. The yields are shown for $B^0 \rightarrow K^{\ast 0}\tau\tau$ signal and the two background components ($B\bar{B}$ decays and $q\bar{q}$ continuum).
Distribution of the di-tau invariant mass squared $q^2$ assumed for the generated signal $B^0 \rightarrow K^{\ast 0}\tau\tau$ events.
The formation of light (anti)nuclei with mass number A of a few units (e.g., d, $^3$He, and $^4$He) in high-energy hadronic collisions presents a longstanding mystery in nuclear physics [1,2]. It is not clear how nuclei bound by a few MeV can emerge in environments characterized by temperatures above 100 MeV [3-5], about 100,000 times hotter than the center of the Sun. Despite extensive studies, this question remained unanswered. The ALICE Collaboration now addresses it with a novel approach using deuteron-pion momentum correlations in proton-proton (pp) collisions at the Large Hadron Collider (LHC). Our results provide model-independent evidence that about 80% of the observed (anti)deuterons are produced in nuclear fusion reactions [6] following the decay of short-lived resonances, such as the $\Delta (1232)$. These findings resolve a crucial gap in our understanding of nucleosynthesis in hadronic collisions. Beyond answering the fundamental question on how nuclei are formed in hadronic collisions, the results can be employed in the modeling of the production of light and heavy nuclei in cosmic rays [7] and dark matter decays [8,9].
Measured $\pi^{+}$–d$\oplus\pi^{-}$–$\overline{\mathrm{d}}$ (left panel) correlation function.
Measured $\pi^{-}$–d$\oplus\pi^{+}$–$\overline{\mathrm{d}}$ (right panel) correlation function.
The extracted kinetic decoupling temperature is derived from $\pi^{+}$–d correlation functions.
The pseudorapidity distribution of charged hadrons produced in Au+Au collisions at a center-of-mass energy of $\sqrt{s_\mathrm{NN}} = 200$ GeV is measured using data collected by the sPHENIX detector. Charged hadron yields are extracted by counting cluster pairs in the inner and outer layers of the Intermediate Silicon Tracker, with corrections applied for detector acceptance, reconstruction efficiency, combinatorial pairs, and contributions from secondary decays. The measured distributions cover $|\eta| < 1.1$ across various centralities, and the average pseudorapidity density of charged hadrons at mid-rapidity is compared to predictions from Monte Carlo heavy-ion event generators. This result, featuring full azimuthal coverage at mid-rapidity, is consistent with previous experimental measurements at the Relativistic Heavy Ion Collider, thereby supporting the broader sPHENIX physics program.
Nch, Npart, and Nch/(Npart/2) values in Table 4, presented in Figure 6.
Nch as a function of $\eta$, presented in Figure 5.
This paper reports measurements of the transverse energy per unit pseudorapidity ($dE_{T}/dη$) produced in Au+Au collisions at $\sqrt{s_{NN}} = 200$ GeV, performed with the sPHENIX detector at the Relativistic Heavy Ion Collider (RHIC). The results cover the pseudorapidity range $\left|η\right| < 1.1$ and constitute the first such measurement performed using a hadronic calorimeter at RHIC. Measurements of $dE_{T}/dη$ are presented for a range of centrality intervals and the average $dE_{T}/dη$ as a function of the number of participating nucleons, $N_{\mathrm{part}}$, is compared to a variety of Monte Carlo heavy-ion event generators. The results are in agreement with previous measurements at RHIC, and feature an improved granularity in $η$ and improved precision in low-$N_{\mathrm{part}}$ events.
An example of a reconstructed EMCal di-cluster invariant mass distribution, similar to those used for in situ EMCal tower calibrations. The distributions are made from EMCal cluster pairs using Run 2024 Au+Au data. The prominent peak arises from $\pi^{0}\to\gamma\gamma$ decays.
An example of a reconstructed EMCal di-cluster invariant mass distribution, similar to those used for in situ EMCal tower calibrations. The distributions are made from EMCal cluster pairs using a GEANT-4 simulation of HIJING events. The prominent peak arises from $\pi^{0}\to\gamma\gamma$ decays.
An example of the measured energy distribution in a single OHCal tower, showing the MIP distribution from cosmic-ray data from the detector.
Partonic collectivity is one of the necessary signatures for the formation of quark-gluon plasma in high-energy nuclear collisions. Number of constituent quarks (NCQ) scaling has been observed for hadron elliptic flow $v_2$ in top energy nuclear collisions at the Relativistic Heavy Ion Collider and the LHC, and this has been theoretically suggested as strong evidence for partonic collectivity. In this Letter, a systematic analysis of $v_2$ of $π^{\pm}$, $K^{\pm}$, $K^{0}_{S}$, $p$, and $Λ$ in Au+Au collisions at ${\sqrt{s_{_{\rm{NN}}}}}$ = 3.2, 3.5, 3.9, and 4.5 GeV, with the STAR experiment at the Relativistic Heavy Ion Collider, is presented. NCQ scaling is markedly violated at 3.2 GeV, consistent with a hadronic-interaction dominated equation of state. However, as the collision energy increases, a gradual evolution to NCQ scaling is observed. This beam-energy dependence of $v_2$ for all hadrons studied provides evidence for the onset of dominant partonic interactions by ${\sqrt{s_{_{\rm{NN}}}}}$ = 4.5 GeV.
$p_{T}$ dependence of $v_{2}$ for $\pi^{+}$ in Au+Au collisions at 3 GeV
$p_{T}$ dependence of $v_{2}$ for $\pi^{+}$ in Au+Au collisions at 3.2 GeV
$p_{T}$ dependence of $v_{2}$ for $\pi^{+}$ in Au+Au collisions at 3.5 GeV