BaBar Research Articles

Investigation of vertex a1>>VP for hadronic tau decays

In the framework of U(3) symmetric quark model, triangular diagrams are calculated that describe the strongly interacting vertices a1>>rhopi and a1>>K*K. The divergences arising when considering quark loops are regularized by covariant cutoff parameter. Based on four-particle hadronic τ decays, the quark structure of the resonance with quantum numbers JPC=1++ was studied. Theoretical estimates of intermediate channels with the meson for the partial decay widths of tau>>pipipinu, tau>>KKpinu and tau>>KKetanu are obtained. Contributions from contact channels describing the direct production of 3pi, KKpi and KKeta mesons by τ lepton current are taken into account. The interference of contact and intermediate axial-vector channels in determining the integral decay widths is studied. The matrix elements of the processes are obtained in the leading approximation of 1/Nc expansion. It is shown that calculations on τ lepton mesonic decays confirm the quark-antiquark structure of the a1 meson and clarify the role of the intermediate non-strange axial-vector channel in determining the integral partial decay widths. The obtained results are compared with experimental data by BaBar and Belle collaborations at the BEPC II and KEK lepton colliders.

Determination of the resonant parameters of with global fit*

Abstract Particle was first observed by the Belle experiment in the invariant mass spectrum in the process and subsequently confirmed by the BaBar experiment. Both experiments reported the resonant parameters of this particle in the processes and assuming as an S-wave Breit-Wigner resonance. We performed a global fit to the distributions of invariant mass of measured by the Belle and BaBar experiments and additionally incorporated the measurements reported by the LHCb experiment to extract the mass and width of . We obtained MeV/ and MeV, which are consistent with the values from PDG within one standard deviation but with higher precision.

Search for the Y(2175) in photoproduction at GlueX

Abstract. The Y(2175), recently renamed to ϕ(2170), is one of the rare exotic candidates connected to strangeonium as compared to the heavier charmonium-like and bottomonium-like exotic states. Originally observed in initial state radiation events by the BaBar experiment in 2006, it is suggested to be a strange partner state of the charmonium-like exotic vector state Y(4230) that was one of the first of the so-called XYZ states reported in the charmonium mass region. The Y(2175) has been seen in various experiments and decay channels,but it has not yet been searched for in a photo-production experiment. In this talk we report on a measurement of the production cross section of the reaction γ + p → ϕπ+ π− + p based on data recorded by the GlueX experiment in order to search for Y(2175) → ϕπ+π−.>

BABAR’s Experience with the Preservation of Data and Analysis Capabilities

The BABAR experiment collected electron-positron collisions at the SLAC National Accelerator Laboratory (SLAC) from 1999-2008. Although data taking has stopped 15 years ago, the collaboration is still actively doing data analyses, publishing results, and giving presentations at international conferences. Special considerations were needed to do analyses using a computing environment that was developed decades ago. A framework is required that preserves the data, data access, and the capability of doing analyses using a well defined and preserved environment. Also, BABAR’s support by SLAC ended at the beginning of 2021. Fortunately, the High Energy Physics Research Computing group at the University of Victoria (UVic), Canada, offered to provide the new home for the main BABAR computing infrastructure, the Grid Computing Centre Karlsruhe offered to host all data for access by analyses running at UVic, and CERN and the IN2P3 Computing Centre offered to store a backup of all data. This paper presents what was done at BABAR to preserve the data and analysis capabilities and what was needed to move the whole computing infrastructure, including collaboration tools and data files, away from SLAC. It will be shown how BABAR preserved the ability to continue to do data analyses and also have a working collaboration tools infrastructure. This paper will describe on BABAR’s experience with such a big change in its infrastructure and what was learned from it, which may be useful to other experiments which are interested in long term analysis support and data preservation in general.

Radiative decays in covariant confined quark model* *Supported by Ho Chi Minh City University of Technology and Education (T2022-26)

Radiative decays are revisited in light of new experimental data from the BaBar and BESIII Collaborations. The radiative couplings encoding nonperturbative QCD effects are calculated in the framework of the covariant confined quark model developed by us. We compare our results with other theoretical studies and experimental data. The couplings (in ) and calculated in our model agree with the corresponding experimental data and . The most interesting case is the decay , for which a recent prediction based on light-cone sum rules at next-to-leading order deviates from the first (and only to date) lattice QCD result at nearly . Our calculation yields , which falls somehow between the two mentioned results, although it is larger than those predicted in other studies using quark models or QCD sum rules.

Search for Evidence of Baryogenesis and Dark Matter in B^{+}→ψ_{D}+p Decays at BABAR.

A new dark sector antibaryon, denoted ψ_{D}, could be produced in decays of B mesons. This Letter presents a search for B^{+}→ψ_{D}+p (and the charge conjugate) decays in e^{+}e^{-} annihilations at 10.58GeV, using data collected in the BABAR experiment. Data corresponding to an integrated luminosity of 398 fb^{-1} are analyzed. No evidence for a signal is observed. Branching fraction upper limits in the range from 10^{-7}-10^{-5} are obtained at 90% confidence level for masses of 1.0<m_{ψ_{D}}<4.3 GeV/c^{2}. The result is also reinterpreted to provide the first limits on a supersymmetric model with R-parity violation and a light neutralino.

Review of Flavor Anomalies

Lepton flavor universality exists in the Standard Model, and hence any observation of the violation of this universality will be a hint for new physics. Recent experimental searches for processes violating this symmetry have attracted much attention among theorists and experimentalists alike. In recent years, such hints have been observed in flavor changing neutral current weak processes such as b→sll and charged current weak processes such as b→clν processes by collider experiments like Belle, Belle II, BaBar, LHCb, ATLAS, and CMS collaborations, where b,s,c are the bottom, strange, and charm quarks, respectively, and l,ν stand for lepton and the corresponding lepton neutrino, respectively. This article is a review of some of the interesting anomalies observed in the B-sector and includes decays of Bs mesons.

Determination of the resonant parameters of excited vector strangenia with data* *Supported by the National Key R&D Program of China (2022YFA1601903), and the National Natural Science Foundation of China (12175041)

We determine the resonant parameters of the vector states and by performing a combined fit to the cross sections from the threshold to measured by the BaBar, Belle, BESIII, and CMD-3 experiments. The mass and width are obtained for , and the mass and width are obtained for . The statistical significance of is . Depending on the interference between , , and a non-resonant amplitude in the nominal fit, we obtain four solutions and , , or , and , , or . We also search for the production of , and the significance is only . We then determine the upper limit of at the 90% confidence level.

Search for heavy neutral leptons using tau lepton decays at BaBaR

This article presents a model-independent search for an additional, mostly sterile, heavy neutral lepton (HNL), that is capable of mixing with the Standard Model τ neutrino with a mixing strength of |Uτ4|2, corresponding to the absolute square of the extended Pontecorvo-Maki-Nakagawa-Sakata matrix element. Data from the BABAR experiment, with a total integrated luminosity of 424 fb−1, are analyzed using a kinematic approach that makes no assumptions on the model behind the origins of the HNL, its lifetime or decay modes. No significant signal is found. Upper limits on |Uτ4|2 at the 95% confidence level, depend on the HNL mass hypothesis and vary from 2.31×10−2 to 5.04×10−6 (with all uncertainties considered), across the mass range 100<m4<1300 MeV/c2; the more stringent limits being placed at higher masses.3 MoreReceived 21 July 2022Accepted 13 September 2022DOI:https://doi.org/10.1103/PhysRevD.107.052009Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI. Funded by SCOAP3.Published by the American Physical SocietyPhysics Subject Headings (PhySH)Research AreasBaryogenesis & leptogenesisExtensions of fermion sectorNeutrino interactionsNeutrino oscillationsParticle dark matterParticles & Fields

Traces of the new a_0(1780) resonance in the J/psi rightarrow phi K^+K^-(K^0bar{K}^0) reaction

We study the J/psi rightarrow phi K bar{K} decay, looking for differences in the production rates of K^+ K^- or K^0 bar{K}^0 in the region of 1700–1800 MeV, where two resonances appear dynamically generated from the vector-vector interaction. Two resonances are known experimentally in that region, the f_0(1710) and a new resonance reported by the BABAR and BESIII collaborations. The K bar{K} should be produced with I=0 in that reaction, but due to the different K^{*0} and K^{*+} masses some isospin violation appears. Yet, due to the large width of the K^*, the violation obtained is very small and the rates of K^+ K^- or K^0 bar{K}^0 production are equal within 5%. However, we also find that due to the step needed to convert two vectors into K bar{K}, a shape can appear in the K bar{K} mass distribution that can mimic the a_0 production around the K^* bar{K}^* threshold, and is simply a threshold effect.

Impact of Λb→Λcτν measurement on new physics in b→clν transitions

Measurements of the branching ratios of $B \to D^{(*)}\tau\bar\nu/B \to D^{(*)}\ell\bar\nu$ and $B_c\to J/\psi\, \tau\bar\nu/B_c\to J/\psi\, \ell\bar\nu$ by the BaBar, Belle and LHCb collaborations consistently point towards an abundance of taus compared to channels with light leptons. However, the ratio $\Lambda_b \to\Lambda_c \tau\bar\nu/\Lambda_b \to\Lambda_c \ell\bar\nu$ shows a relative deficit in taus. In this paper, we critically address whether data still points towards a coherent pattern of deviations, in particular in light of the sum rule relating these decays in a model-independent way. We find that no common new physics explanation of all ratios is possible (within $2\sigma$ or $1.5\sigma$, depending on the ${\cal R}(\Lambda_c)$ normalization to light lepton channels). While this inconsistency could be a statistical fluctuation, further measurements are required in order to converge to a coherent pattern of experimental results.

Exotics from QCD Sum Rules

Many new exotic states in the charmonium mass region were discovered in the last decades by BaBar, Belle, CLEO-c, CDF, DØ, BESIII, LHCb and CMS Collaborations. We use the QCD Sum Rule approach to study some of these states.

Singlet vector leptoquark model facing recent LHCb and BABAR measurements

Very recently the LHCb experiment released the first measurement of the ratio R(Λc)=BR(Λb→Λcτν¯τ)/BR(Λb→Λcμν¯μ). Moreover, the BABAR experiment reported a new result of the leptonic decay ratio of Upsilon meson ϒ(3S), namely, Rϒ(3S)=BR(ϒ(3S)→τ+τ−)/BR(ϒ(3S)→μ+μ−). Both measurements are below their corresponding Standard Model predictions (deficit), deviating by ∼1.1σ and ∼1.8σ, respectively. In addition, the LHCb recently presented the first search of the lepton flavor violating decay B0→K⁎0μ±τ∓. Motivated by these new data, in this work we study their impact on the phenomenology of the singlet vector leptoquark (U1) model addressing the hints of lepton flavor universality violation in the semileptonic decays of B mesons (B meson anomalies), by carrying out a global fit analysis. In general, we found that a minimal version of the U1 model with a mass of 2 TeV can successfully explain the B meson anomalies, while being compatible with all other flavor observables and LHC bounds. Interestingly, our study shows that the new observables R(Λc) and Rϒ(3S) generate strong tension, leading to non-trivial effects on the global fit. Future improvements at the LHCb and Belle II experiments would help to understand their complementary. Moreover, we also analyze the impact of the expected sensitivity on flavor observables at Belle II to provide a further test of the U1 model. Finally, we study the minimal assumptions under which the U1 model could, in addition, provide a combined explanation of the anomalous magnetic moment of the muon.

Repercussion of the [formula omitted] [[formula omitted]] resonance and future developments

In this paper, we discuss the significance and prospect for the newly discovered a0(1710)[a0(1817)] resonance state at BESIII experiment, in which they reported the observation of a scalar meson of spin-parity $J^P=0^+$ with isospin $I=1$, branded as $a_0(1817)$. This state may be the same particle as the $a_0(1710)$ observed by the BaBar experiment earlier. As early as 2008, we found that f0(1710) can be regarded as a $K^* \bar{K}^*$ molecular state based on the chiral unitary theory, and there is a partner state $a_0(1710)$ with an isospin $I=1$. Our theoretical prediction based on this picture is in good agreement with the latest BESIII data, which further supports the molecular state picture of $a_0(1710)[a_0(1817)]$. If it is indeed the isospin partner state of $f_0(1710)$, this would rule out $f_0(1710)$ as a glueball candidate. This paper briefly reviews the relevant theoretical studies and suggests new experiments to further examine the nature of $a_0(1710)[a_0(1817)]$.

Broad resonance structure in e+e−→f1(1285)π+π− and higher ρ -meson excitations

Recently, the BaBar Collaboration reported a broad resonance structure near 2 GeV when analyzing the $e^+e^-\to f_1(1285)\pi^+\pi^-$ process, which provides a good opportunity to study the higher $\rho$-mesonic states. When considering the $\rho(1900)$ and $\rho(2150)$ contributions, the experimental data of the cross section of $e^+e^-\to f_1(1285)\pi^+\pi^-$ around 2 GeV can be well depicted, especially the observed broad resonance structure in $e^+e^-\to f_1(1285)\pi^+\pi^-$ containing two substructures is suggested by the present work. Additionally, we also indicate a possible signal of $\rho(5S)$ around 2.5 GeV in the $e^+e^-\to f_1(1285)\pi^+\pi^-$ process. The obtained result may provide a valuable hint to identify higher $\rho$ mesons, which will be a new task for the BESIII and Belle II experiments with the accumulation of higher precision data.

Measurement of J/psi decays into final states 2(pi ^{+}pi ^{-})pi ^{0},K^{+}K^{-}pi ^{+}pi ^{-}pi ^{0},,2(pi ^{+}pi ^{-}) and K^{+}K^{-}pi ^{+}pi ^{-}

Using the 1.32 hbox {pb}^{-1} statistics collected at the J/psi peak with the KEDR detector at the VEPP-4M e^{+}e^{-, }collider, we measured the branching fractions of J/psi meson decays to the final states 2(pi ^{+}pi ^{-})pi ^{0}, K^{+}K^{-}pi ^{+}pi ^{-}pi ^{0}, 2(pi ^{+}pi ^{-}) and K^{+}K^{-}pi ^{+}pi ^{-}. The results obtained for the decays J/psi rightarrow 2(pi ^{+}pi ^{-})pi ^{0}, J/psi rightarrow K^{+}K^{-}pi ^{+}pi ^{-}pi ^{0} contradict the measurements performed by other groups in the last century, but agree well with recent results of BABAR and BESIII collaborations.

The rho meson timelike electromagnetic form factors in kT factorization approach

In this paper, we calculate the [Formula: see text]-meson timelike electromagnetic form factors by employing the [Formula: see text] factorization approach. The theoretical ratio for the moduli of three helicity amplitudes and total cross-section for the annihilation/production process [Formula: see text] are analyzed at [Formula: see text], where the BaBar experiment was done. The results for the moduli of the three helicity amplitudes [Formula: see text] are predicted between [Formula: see text] and [Formula: see text], and the three form factors [Formula: see text] of rho meson are considered.

Search for invisible dark photon in gamma e scattering at future lepton colliders

For the first time, the production of a massive dark photon (DP) in the gamma e^- scattering at the future lepton colliders ILC, CLIC, and CEPC is examined. The invisible decay mode of the DP is addressed. We have studied both the unpolarized scattering and the collision of the Compton backscattered photons with the polarized electron. The missing energy distributions are shown. We have considered the wide range 1–1000 GeV of the DP mass m_{A'}. The excluded regions at the 95% CL in the plane (varepsilon , m_{A'}), where varepsilon is the kinetic mixing parameter, are obtained. In particular, in the low mass region, 1–10 GeV our bounds for the 90 GeV CEPC are several times stronger than experimental limits obtained by the BaBar collaboration. For the polarized scattering, the excluded bounds for all three colliders are approximately 20% stronger as compared with the unpolarized case.

Cross section measurements of the e+e−→ D*+D*− and e+e−→ D*+D− processes at center-of-mass energies from 4.085 to 4.600 GeV

The Born cross sections of the e+e−→ D*+D*− and e+e−→ D*+D− processes are measured using e+e− collision data collected with the BESIII experiment at center-of-mass energies from 4.085 to 4.600 GeV, corresponding to an integrated luminosity of 15.7 fb−1. The results are consistent with and more precise than the previous measurements by the Belle, Babar and CLEO collaborations. The measurements are essential for understanding the nature of vector charmonium and charmonium-like states.

Search for an Axionlike Particle in B Meson Decays.

Axionlike particles (ALPs) are predicted in many extensions of the standard model, and their masses can naturally be well below the electroweak scale. In the presence of couplings to electroweak bosons, these particles could be emitted in flavor-changing B meson decays. We report herein a search for an ALP, a, in the reaction B^{±}→K^{±}a, a→γγ using data collected by the BABAR experiment at SLAC. No significant signal is observed, and 90%confidence level upper limits on the ALP coupling to electroweak bosons are derived as a function of ALP mass, improving current constraints by several orders of magnitude in the range 0.175 GeV<m_{a}<4.78 GeV.