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DOE OSTI2024

Nonresonant central exclusive production of charged-hadron pairs in proton-proton collisions at s = 13 TeV

The central exclusive production of charged-hadron pairs in p p collisions at a center-of-mass energy of 13 TeV is examined, based on data collected in a special high- β * run of the LHC. The nonresonant continuum processes are studied with the invariant mass of the centrally produced two-pion system in the resonance-free region, m π + π − < 0.7 or m π + π − > 1.8 GeV . Differential cross sections as functions of the azimuthal angle between the surviving protons, squared exchanged four-momenta, and m π + π − are measured in a wide region of scattered proton transverse momenta, between 0.2 and 0.8 GeV, and for pion rapidities | y | < 2 . A rich structure of interactions related to double-pomeron exchange is observed. A parabolic minimum in the distribution of the two-proton azimuthal angle is observed for the first time. It can be interpreted as an effect of additional pomeron exchanges between the protons from the interference between the bare and the rescattered amplitudes. After model tuning, various physical quantities are determined that are related to the pomeron cross section, proton-pomeron and meson-pomeron form factors, pomeron trajectory and intercept, and coefficients of diffractive eigenstates of the proton. © 2024 CERN, for the CMS and TOTEMs Collaboration 2024 CERN

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2024

New μ forces from ν μ sources

Accelerator-based experiments reliant on charged pion and kaon decays to produce muon-neutrino beams also deliver an associated powerful flux of muons. Therefore, these experiments can additionally be sensitive to light new particles that preferentially couple to muons and decay to visible final states on macroscopic length scales. Such particles are produced through rare 3-body meson decays in the decay pipe or via muon scattering in the beam dump, and decay in a downstream detector. To demonstrate the potential of this search strategy, we recast existing MiniBooNE and MicroBooNE studies of neutral pion production in neutrino-induced neutral-current scattering ( ν μ N → ν μ N π 0 , π 0 → γ γ ) to place limits on light ( < 2 m μ ) muon-philic scalar particles that decay to diphotons through loops of virtual muons. While much of this parameter space has already been excluded by E137, we also project that SBND can be sensitive to unexplored parameter space for these models, and provide a road map for future neutrino experiments to perform dedicated searches for muon-philic forces. Published by the American Physical Society 2024

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2024

Nonlinear Sigma model amplitudes to all loop orders are contained in the Tr ( Φ 3 ) theory

Scattering amplitudes for the simplest theory of colored scalar particles—the Tr ( Φ 3 ) theory—have recently been the subject of active investigations. In this work we describe an unanticipated wider implication of this work: the Tr ( Φ 3 ) theory secretly contains nonlinear sigma model (NLSM) amplitudes to all loop orders. The NLSM amplitudes are obtained from Tr ( Φ 3 ) amplitudes by a unique shift of kinematic variables. We show that this shifted kinematics produces amplitudes for a cubic theory with a linear term in the potential, with extrema spontaneously breaking U ( N ) → U ( N − k ) × U ( k ) . The Goldstone amplitudes for this theory coincide with those of pions in the U ( N ) × U ( N ) → U ( N ) chiral Lagrangian to all orders in the planar limit. We also give a purely on-shell understanding of this correspondence, showing that integrands defined by the kinematic shifts have the correct residues on poles and appropriately produce the Adler zero. Finally, we discuss how similar kinematic shifts produce certain infinite classes of mixed amplitudes of pions and Tr ( Φ 3 ) scalars, most of which are not interpretable from the Lagrangian description. Published by the American Physical Society 2024

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2024

Dissecting a strongly coupled scalar nucleon

We continue our investigation of the stress within a strongly coupled scalar nucleon, and now dissect the gravitational form factors into contributions from its constituents, the (mock) nucleon and the (mock) pion. The computation is based on a nonperturbative solution of the scalar Yukawa model in the light-front Hamiltonian formalism with a Fock sector expansion, including up to one nucleon and two pions. By employing the “good currents” T i + + , T i + − and T i 12 , we extract the full set of gravitational form factors A i , D i , c ¯ i without the contamination of the spurious form factors and free of uncanceled UV divergences. With these results, we decompose the mass of the system into its constituents and compute the matter and mechanical radii, gaining insights into the strongly coupled system. Published by the American Physical Society 2024

Cao, Xianghui (ORCID:0009000359096713)↗

DOE OSTI2024

Timelike meson form factors beyond the elastic region from lattice QCD

We present a calculation of the vector-isovector timelike form factors of the pion and the kaon using lattice quantum chromodynamics. We calculate two-point correlation functions with m π ∼ 280 MeV , extracting both the finite-volume spectrum and matrix elements for these states created from the vacuum by a vector current. After determining the coupled-channel π π , K K ¯ scattering amplitudes, we perform the necessary correction for the significant finite-volume effects present in the current matrix elements, leading to the timelike form factors. We find these to be dominated by the presence of the ρ resonance, and we extract its decay constant by an analytic continuation of the amplitudes to the resonance pole. In addition, the spacelike pion form factor is determined on the same lattice configurations, and a dispersive parametrization is used to simultaneously describe the spacelike and elastic timelike regions. Published by the American Physical Society 2024

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2024

Bootstrapping gauge theories

We consider asymptotically free gauge theories with gauge group S U ( N c ) and N f quarks with mass m q ≪ Λ QCD that undergo chiral symmetry breaking and confinement. We propose a bootstrap method to compute the S matrix of the pseudo-Goldstone bosons (pions) that dominate the low-energy physics. For the important case of N c = 3 , N f = 2 , a numerical implementation of the method gives the phase shifts of the S 0 , P 1 and S 2 waves in good agreement with experimental results. The method incorporates gauge theory information ( N c , N f , m q , Λ QCD ) by using the form-factor bootstrap recently proposed by Karateev, Kuhn and Penedones together with a finite energy version of the Shifman-Vainshtein-Zakharov (SVZ) sum rules. At low energy we impose constraints from chiral symmetry breaking. The only low-energy numerical inputs are the pion mass m π and the quark and gluon condensates. Published by the American Physical Society 2024

He, Yifei (ORCID:0000000213666157)↗

DOE OSTI2025

QCD moat regime and its real-time properties

Dense quantum chromodynamics (QCD) matter may exhibit crystalline phases. Their existence is reflected in a moat regime, where mesonic correlations feature spatial modulations. We study the real-time properties of pions at finite temperature and density in QCD in order to elucidate the nature of this regime. We show that the moat regime arises from particle-hole-like fluctuations near the Fermi surface. This gives rise to a characteristic peak in the spectral function of the pion at nonzero spacelike momentum. This peak can be interpreted as a new quasi particle, the moaton. In addition, our framework also allows us to directly test the stability of the homogeneous chiral phase against the formation of an inhomogeneous condensate in QCD. We find that an inhomogeneous instability is highly unlikely for baryon chemical potentials μ B ≤ 630 MeV . Published by the American Physical Society 2025

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗

DOE OSTI2013

Direct Measurement of the Bubble Nucleation Energy Threshold in a CF3I Bubble Chamber

Here, we measured the energy threshold and efficiency for bubble nucleation from iodine recoils in a CF 3 I bubble chamber in the energy range of interest for a dark matter search. These interactions cannot be probed by standard neutron calibration methods, so we develop a new technique by observing the elastic scattering of 12 GeV/c negative pions. The pions are tracked with a silicon pixel telescope and the reconstructed scattering angle provides a measure of the nuclear recoil kinetic energy. The bubble chamber was operated with a nominal threshold of (13.6±0.6) keV. Interpretation of the results depends on the response to fluorine and carbon recoils, but in general we find agreement with the predictions of the classical bubble-nucleation theory. Moreover, this measurement confirms the applicability of CF 3 I as a target for spin-independent dark matter interactions and represents a novel technique for calibration of superheated fluid detectors.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗

DOE OSTI2013

Study of exclusive B → X u ℓ ν decays and extraction of | V u b | using full reconstruction tagging at the Belle experiment

Here, we report the results of a study of the exclusive semileptonic decays B - → π 0 ℓ - ν ¯ ℓ , B ¯ 0 → π + ℓ - ν ¯ ℓ , B - → ρ 0 ℓ - ν ¯ ℓ , B ¯ 0 → ρ + ℓ - ν ¯ ℓ and B - → ω ℓ - ν ¯ ℓ , where ℓ represents an electron or a muon. The events are tagged by fully reconstructing a second B meson in the event in a hadronic decay mode. The measured branching fractions are B ( B - → π 0 ℓ - ν ¯ ℓ ) = ( 0.80 ± 0.08 ± 0.04 ) × 10 - 4 , B ( B ¯ 0 → π + ℓ - ν ¯ ℓ ) = ( 1.49 ± 0.09 ± 0.07 ) × 10 - 4 , B ( B - → ρ 0 ℓ - ν ¯ ℓ ) = ( 1.83 ± 0.10 ± 0.10 ) × 10 - 4 , B ( B ¯ 0 → ρ + ℓ - ν ¯ ℓ ) = ( 3.22 ± 0.27 ± 0.24 ) × 10 - 4 , and B ( B - → ω ℓ - ν ¯ ℓ ) = ( 1.07 ± 0.16 ± 0.07 ) × 10 - 4 , where the first error is statistical and the second one is systematic. The obtained branching fractions are inclusive of soft photon emission. Furthermore, we determine the branching fractions as a function of the 4-momentum transfer squared to the leptonic system q 2 = ( p ℓ + p ν ) 2 , where p ℓ and p ν are the lepton and neutrino 4-momenta, respectively. Using the pion modes, a recent light cone sum rule calculation, lattice QCD results and a model-independent description of the hadronic form factor, a value of the Cabibbo-Kobayashi-Maskawa matrix element | V u b | = ( 3.52 ± 0.29 ) × 10 - 3 is extracted. A structure in the two-pion invariant mass distribution near 1.3 GeV / c 2 , which might be dominated by the decay B - → f 2 ( 1270 ) ℓ - ν ¯ ℓ , f 2 → π + π - , is seen. These results are obtained from a 711 fb - 1 data sample that contains 772 × 10 6 B B ¯ pairs, collected near the Υ ( 4 S ) resonance with the Belle detector at the KEKB asymmetric-energy e + e - collider.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2013

Baryon masses at nonzero isospin/kaon density

We propose a lattice QCD calculation of the ground-state energy shifts of various baryons in a medium of pions or kaons at a single value of the quark mass corresponding to a pion mass of m π ~390 MeV and a kaon mass of m K ~540 MeV, and in a spatial volume V ~ (4 fm) 3 . All systems are made using a canonical formalism in which quark propagators are contracted into correlation functions of fixed isospin/kaon density. We examine four different systems, Σ + (π + ) n , Ξ 0 (π + ) n , p(K + ) n , and n(K + ) n , for up to n = 11 mesons. From the ground-state energy shifts we extract two- and three-body scattering parameters, as well as linear combinations of low-energy constants appearing in tree-level chiral perturbation theory.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2014

Comprehensive amplitude analysis of γ γ → π + π - , π 0 π 0 and K ¯ K below 1.5 GeV

In this paper we perform an amplitude analysis of essentially all published pion and kaon pair production data from two photon collisions below 1.5 GeV. This includes all the high statistics results from Belle, as well as older data from Mark II at SLAC, CELLO at DESY, Crystal Ball at SLAC. The purpose of this analysis is to provide as close to a model-independent determination of the γγ to meson pair amplitudes as possible. Having data with limited angular coverage, typically |cosθ| < 0.6-0.8, and no polarization information for reactions in which spin is an essential complication, the determination of the underlying amplitudes might appear an intractable problem. However, imposing the basic constraints required by analyticity, unitarity, and crossing-symmetry makes up for the experimentally missing information. Above 1.5 GeV multi-meson production channels become important and we have too little information to resolve the amplitudes. Nevertheless, below 1.5 GeV the two photon production of hadron pairs serves as a paradigm for the application of S-matrix techniques. Final state interactions among the meson pairs is critical to this analysis. To fix these, we include the latest ππ → ππ, K⁻K scattering amplitudes given by dispersive analyses, supplemented in the K⁻K threshold region by the recent precision Dalitz plot analysis from BaBar. With these hadronic amplitudes built into unitarity, we can constrain the overall description of γγ → ππ and K⁻K datasets, both integrated and differential cross-sections, including the high statistics charged and neutral pion data from Belle. A region of solutions is found for the γγ → ππ partial waves with both isospin 0 and 2. Since this analysis invokes coupled hadronic channels, even the relatively poor integrated cross-section data on γγ → K⁻K narrows the patch of solutions to essentially a single form. For this we present the complete partial wave amplitudes, show how well they fit all the available data, and give the two photon couplings of scalar and tensor resonances that appear.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2014

Charmed bottom baryon spectroscopy from lattice QCD

In this study, we calculate the masses of baryons containing one, two, or three heavy quarks using lattice QCD. We consider all possible combinations of charm and bottom quarks, and compute a total of 36 different states with J P = 1/2 + and J P = 3/2 + . We use domain-wall fermions for the up, down, and strange quarks, a relativistic heavy-quark action for the charm quarks, and nonrelativistic QCD for the bottom quarks. Our analysis includes results from two different lattice spacings and seven different pion masses. We perform extrapolations of the baryon masses to the continuum limit and to the physical pion mass using SU(4|2) heavy-hadron chiral perturbation theory including 1/m Q and finite-volume effects. For the 14 singly heavy baryons that have already been observed, our results agree with the experimental values within the uncertainties. We compare our predictions for the hitherto unobserved states with other lattice calculations and quark-model studies.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗

DOE OSTI2015

B -meson decay constants from 2 + 1 -flavor lattice QCD with domain-wall light quarks and relativistic heavy quarks

We calculate the B-meson decay constants f B , f B s , and their ratio in unquenched lattice QCD using domain-wall light quarks and relativistic b quarks. We use gauge-field ensembles generated by the RBC and UKQCD collaborations using the domain-wall fermion action and Iwasaki gauge action with three flavors of light dynamical quarks. We analyze data at two lattice spacings of a ≈ 0.11, 0.086 fm with unitary pion masses as light as M π ≈ 290 MeV; this enables us to control the extrapolation to the physical light-quark masses and continuum. For the b quarks we use the anisotropic clover action with the relativistic heavy-quark interpretation, such that discretization errors from the heavy-quark action are of the same size as from the light-quark sector. We renormalize the lattice heavy-light axial-vector current using a mostly nonperturbative method in which we compute the bulk of the matching factor nonperturbatively, with a small correction, that is close to unity, in lattice perturbation theory. We also improve the lattice heavy-light current through O(α s a). We extrapolate our results to the physical light-quark masses and continuum using SU(2) heavy-meson chiral perturbation theory, and provide a complete systematic error budget. We obtain f B 0 = 199.5(12.6) MeV, f B + =195.6(14.9) MeV, f B s =235.4(12.2) MeV, f B s /f B 0 =1.197(50), and f B s /f B + =1.223(71), where the errors are statistical and total systematic added in quadrature. Finally, these results are in good agreement with other published results and provide an important independent cross-check of other three-flavor determinations of B-meson decay constants using staggered light quarks.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2015

Measurement of muon plus proton final states in ν μ interactions on hydrocarbon at < E ν > = 4.2 GeV

A study of charged-current muon neutrino scattering on hydrocarbon in which the final state includes a muon, at least one proton, and no pions is presented. Although this signature has the topology of neutrino quasielastic scattering from neutrons, the event sample contains contributions from quasielastic and inelastic processes where pions are absorbed in the nucleus. The analysis accepts events with muon production angles up to 70° and proton kinetic energies greater than 110 MeV. The cross section, when based completely on hadronic kinematics, is well described by a relativistic Fermi gas nuclear model including the neutrino event generator modeling for inelastic processes and particle transportation through the nucleus. This is in contrast to the quasielastic cross section based on muon kinematics, which is best described by an extended model that incorporates multinucleon correlations. As a result, this measurement guides the formulation of a complete description of neutrino-nucleus interactions that encompasses the hadronic as well as the leptonic aspects of this process.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2015

$B \to \pi \ell \nu$ and $B_s \to K \ell \nu$ form factors and $|V_{ub}|$ from 2+1-flavor lattice QCD with domain-wall light quarks and relativistic heavy quarks

We calculate the form factors for B → πℓν and B s → Kℓν decay in dynamical lattice quantum chromodynamics (QCD) using domain-wall light quarks and relativistic b-quarks. We use the (2+1)-flavor gauge-field ensembles generated by the RBC and UKQCD collaborations with the domain-wall fermion action and Iwasaki gauge action. For the b-quarks we use the anisotropic clover action with a relativistic heavy-quark interpretation. We analyze data at two lattice spacings of a ≈ 0.11, 0.086 fm with unitary pion masses as light as M π ≈ 290 MeV. We simultaneously extrapolate our numerical results to the physical light-quark masses and to the continuum and interpolate in the pion/kaon energy using SU(2) “hard-pion” chiral perturbation theory for heavy-light meson form factors. We provide complete systematic error budgets for the vector and scalar form factors f + (q 2 ) and f 0 (q 2 ) for both B → πℓν and B s → Kℓν at three momenta that span the q 2 range accessible in our numerical simulations. Next we extrapolate these results to q 2 = 0 using a model-independent z-parametrization based on analyticity and unitarity. We present our final results for f + (q 2 ) and f 0 (q 2 )as the coefficients of the series in z and the matrix of correlations between them; this provides a parametrization of the form factors valid over the entire allowed kinematic range. Our results agree with other three-flavor lattice-QCD determinations using staggered light quarks, and have comparable precision, thereby providing important independent cross-checks. Both B → πℓν and B s → Kℓν decays enable determinations of the Cabibbo-Kobayashi-Maskawa matrix element |V ub |. Furthermore, we perform a combined z-fit of our numerical B → πℓν form-factor data with the experimental measurements of the branching fraction from BABAR and Belle leaving the relative normalization as a free parameter; we obtain |V ub | = 3.61(32)×10 -3 , where the error includes statistical and all systematic uncertainties. The same approach can be applied to the decay B s → Kℓν to provide an alternative determination of |V ub | once the process has been measured experimentally. In anticipation of future experimental measurements, we make predictions for B → πℓν and B s → Kℓν differential branching fractions and forward-backward asymmetries in the Standard Model.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2015

Λ b → p ℓ - ν ¯ ℓ and Λ b → Λ c ℓ - ν ¯ ℓ form factors from lattice QCD with relativistic heavy quarks

Measurements of the Λ b → p ℓ - ν ¯ ℓ and Λ b → Λ c ℓ - ν ¯ ℓ decay rates can be used to specify the magnitudes of the Cabibbo-Kobayashi-Maskawa matrix elements Vub and Vcb, provided that the relevant hadronic form factors are known. In this work we present a precise calculation of these form factors using lattice QCD with 2 + 1 flavors of dynamical domain-wall fermions. The b and c quarks are implemented with relativistic heavy-quark actions, allowing us to work directly at the physical heavy-quark masses. The lattice computation is performed for six different pion masses and two different lattice spacings, using gauge-field configurations generated by the RBC and UKQCD Collaborations. The b → u and b → c currents are renormalized with a mostly nonperturbative method. We extrapolate the form factor results to the physical pion mass and the continuum limit, parametrizing the q 2 dependence using z expansions. The form factors are presented in such a way as to enable the correlated propagation of both statistical and systematic uncertainties into derived quantities such as differential decay rates and asymmetries. Using these form factors, we present predictions for the Λ b → p ℓ - ν ¯ ℓ and Λ b → Λ c ℓ - ν ¯ ℓ differential and integrated decay rates. Combined with experimental data, our results enable determinations of |V ub |, |V cb |, and |V ub /V cb | with theory uncertainties of 4.4%, 2.2%, and 4.9%, respectively.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2015

Fragmentation functions at next-to-next-to-leading order accuracy

We present a first analysis of parton-to-pion fragmentation functions at next-to-next-to-leading order accuracy in QCD based on single-inclusive pion production in electron-positron annihilation. Special emphasis is put on the technical details necessary to perform the QCD scale evolution and cross section calculation in Mellin moment space. Lastly, we demonstrate how the description of the data and the theoretical uncertainties are improved when next-to-next-to-leading order QCD corrections are included.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2016

Inclusive cross section and double-helicity asymmetry for $\pi^{0}$ production at midrapidity in $p$$+$$p$ collisions at $\sqrt{s}=510$ GeV

PHENIX measurements are presented for the cross section and double-helicity asymmetry (ALL) in inclusive π⁰ production at midrapidity from p+p collisions at √s = 510 GeV from data taken in 2012 and 2013 at the Relativistic Heavy Ion Collider. The next-to-leading-order perturbativequantum- chromodynamics theory calculation is in excellent agreement with the presented cross section results. The calculation utilized parton-to-pion fragmentation functions from the recent DSS14 global analysis, which prefer a smaller gluon-to-pion fragmentation function. The π⁰A LL results follow an increasingly positive asymmetry trend with pT and √s with respect to the predictions and are in excellent agreement with the latest global analysis results. This analysis incorporated earlier results on π0 and jet A LL , and suggested a positive contribution of gluon polarization to the spin of the proton ΔG for the gluon momentum fraction range x > 0.05. The data presented here extend to a currently unexplored region, down to x 0.01, and thus provide additional constraints on the value of ΔG.

43 PARTICLE ACCELERATORS↗