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  1. Article ; Online: Ruling Out the Massless Up-Quark Solution to the Strong CP Problem by Computing the Topological Mass Contribution with Lattice QCD.

    Alexandrou, Constantia / Finkenrath, Jacob / Funcke, Lena / Jansen, Karl / Kostrzewa, Bartosz / Pittler, Ferenc / Urbach, Carsten

    Physical review letters

    2020  Volume 125, Issue 23, Page(s) 232001

    Abstract: The infamous strong CP problem in particle physics can in principle be solved by a massless up quark. In particular, it was hypothesized that topological effects could substantially contribute to the observed nonzero up-quark mass without reintroducing ... ...

    Abstract The infamous strong CP problem in particle physics can in principle be solved by a massless up quark. In particular, it was hypothesized that topological effects could substantially contribute to the observed nonzero up-quark mass without reintroducing CP violation. Alternatively to previous work using fits to chiral perturbation theory, in this Letter, we bound the strength of the topological mass contribution with direct lattice QCD simulations, by computing the dependence of the pion mass on the dynamical strange-quark mass. We find that the size of the topological mass contribution is inconsistent with the massless up-quark solution to the strong CP problem.
    Language English
    Publishing date 2020-12-18
    Publishing country United States
    Document type Journal Article
    ZDB-ID 208853-8
    ISSN 1079-7114 ; 0031-9007
    ISSN (online) 1079-7114
    ISSN 0031-9007
    DOI 10.1103/PhysRevLett.125.232001
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  2. Article ; Online: Probing the Energy-Smeared R Ratio Using Lattice QCD.

    Alexandrou, Constantia / Bacchio, Simone / De Santis, Alessandro / Dimopoulos, Petros / Finkenrath, Jacob / Frezzotti, Roberto / Gagliardi, Giuseppe / Garofalo, Marco / Hadjiyiannakou, Kyriakos / Kostrzewa, Bartosz / Jansen, Karl / Lubicz, Vittorio / Petschlies, Marcus / Sanfilippo, Francesco / Simula, Silvano / Tantalo, Nazario / Urbach, Carsten / Wenger, Urs

    Physical review letters

    2023  Volume 130, Issue 24, Page(s) 241901

    Abstract: We present a first-principles lattice QCD investigation of the R ratio between the e^{+}e^{-} cross section into hadrons and into muons. By using the method of Ref. [1], that allows one to extract smeared spectral densities from Euclidean correlators, we ...

    Abstract We present a first-principles lattice QCD investigation of the R ratio between the e^{+}e^{-} cross section into hadrons and into muons. By using the method of Ref. [1], that allows one to extract smeared spectral densities from Euclidean correlators, we compute the R ratio convoluted with Gaussian smearing kernels of widths of about 600 MeV and central energies from 220 MeV up to 2.5 GeV. Our theoretical results are compared with the corresponding quantities obtained by smearing the KNT19 compilation [2] of R-ratio experimental measurements with the same kernels and, by centering the Gaussians in the region around the ρ-resonance peak, a tension of about 3 standard deviations is observed. From the phenomenological perspective, we have not included yet in our calculation QED and strong isospin-breaking corrections, and this might affect the observed tension. From the methodological perspective, our calculation demonstrates that it is possible to study the R ratio in Gaussian energy bins on the lattice at the level of accuracy required in order to perform precision tests of the standard model.
    MeSH term(s) Algorithms ; Normal Distribution ; Vibration
    Language English
    Publishing date 2023-06-30
    Publishing country United States
    Document type Journal Article
    ZDB-ID 208853-8
    ISSN 1079-7114 ; 0031-9007
    ISSN (online) 1079-7114
    ISSN 0031-9007
    DOI 10.1103/PhysRevLett.130.241901
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  3. Article ; Online: Quark and Gluon Momentum Fractions in the Pion from N_{f}=2+1+1 Lattice QCD.

    Alexandrou, Constantia / Bacchio, Simone / Bergner, Georg / Finkenrath, Jacob / Gasbarro, Andrew / Hadjiyiannakou, Kyriakos / Jansen, Karl / Kostrzewa, Bartosz / Ottnad, Konstantin / Petschlies, Marcus / Pittler, Ferenc / Steffens, Fernanda / Urbach, Carsten / Wenger, Urs

    Physical review letters

    2022  Volume 127, Issue 25, Page(s) 252001

    Abstract: We perform the first full decomposition of the pion momentum into its gluon and quark contributions. We employ an ensemble generated by the Extended Twisted Mass Collaboration with N_{f}=2+1+1 Wilson twisted mass clover fermions at maximal twist tuned to ...

    Abstract We perform the first full decomposition of the pion momentum into its gluon and quark contributions. We employ an ensemble generated by the Extended Twisted Mass Collaboration with N_{f}=2+1+1 Wilson twisted mass clover fermions at maximal twist tuned to reproduce the physical pion mass. We present our results in the MS[over ¯] scheme at 2 GeV. We find ⟨x⟩_{u+d}=0.601(28), ⟨x⟩_{s}=0.059(13), ⟨x⟩_{c}=0.019(05), and ⟨x⟩_{g}=0.52(11) for the separate contributions, respectively, whose sum saturates the momentum sum rule.
    Language English
    Publishing date 2022-01-14
    Publishing country United States
    Document type Journal Article
    ZDB-ID 208853-8
    ISSN 1079-7114 ; 0031-9007
    ISSN (online) 1079-7114
    ISSN 0031-9007
    DOI 10.1103/PhysRevLett.127.252001
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  4. Book ; Online: Short \& intermediate distance HVP contributions to muon g-2

    Alexandrou, Constantia / Bacchio, Simone / Dimopoulos, Petros / Finkenrath, Jacob / Frezzotti, Roberto / Gagliardi, Giuseppe / Garofalo, Marco / Hadjiyiannakou, Kyriakos / Kostrzewa, Bartosz / Jansen, Karl / Lubicz, Vittorio / Petschlies, Marcus / Sanfilippo, Francesco / Simula, Silvano / Urbach, Carsten / Wenger, Urs

    SM (lattice) prediction versus $e^+e^-$ annihilation data

    2022  

    Abstract: We present new lattice results of the ETM Collaboration, obtained from extensive simulations of lattice QCD with dynamical up, down, strange and charm quarks at physical mass values, different volumes and lattice spacings, concerning the SM prediction ... ...

    Abstract We present new lattice results of the ETM Collaboration, obtained from extensive simulations of lattice QCD with dynamical up, down, strange and charm quarks at physical mass values, different volumes and lattice spacings, concerning the SM prediction for the so-called intermediate window (W) and short-distance (SD) contributions to the leading order hadronic vacuum polarization (LO-HVP) term of the muon anomalous magnetic moment, $a_\mu$. Results for $a_{\mu}^{\rm LO-HVP,W}$ and $a_{\mu}^{\rm LO-HVP,SD}$, besides representing a step forward to a complete lattice computation of $a_{\mu}^{\rm LO-HVP}$ and a useful benchmark among lattice groups, are compared here with their dispersive counterparts based on experimental data for $e^+e^-$ into hadrons. The comparison confirms the tension in $a_{\mu}^{\rm LO-HVP,W}$, already noted in 2020 by the BMW Collaboration, while showing no tension in $a_{\mu}^{\rm LO-HVP,SD}$.

    Comment: Talk given at ICHEP 2022 (6-13 July 2022, Bologna - Italy) - Results here are almost final - Contribution accepted for publication on PoS
    Keywords High Energy Physics - Phenomenology ; High Energy Physics - Lattice
    Subject code 530 ; 612
    Publishing date 2022-12-20
    Publishing country us
    Document type Book ; Online
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