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@ARTICLE{Stump:639335,
      author       = {Stump, Andres and Green, Jeremy Russell},
      title        = {{P}osition-space sampling for local multiquark operators in
                      lattice {QCD} usingdistillation and the importance of
                      tetraquark operators for {T}$_{cc}(3875)^+$},
      reportid     = {PUBDB-2025-04436, DESY-25-140. arXiv:2510.26459.
                      HU-EP-25/35-RTG},
      year         = {2025},
      note         = {16 pages, 7 figures},
      abstract     = {Obtaining hadronic two-point functions is a central step in
                      spectroscopy calculations in lattice QCD. This requires
                      solving the Dirac equation repeatedly, which is
                      computationally demanding. The distillation method addresses
                      this difficulty by using the lowest eigenvectors of the
                      spatial Laplacian to construct a subspace in which the Dirac
                      operator can be fully inverted. This approach is efficient
                      for nonlocal operators such as meson-meson and baryon-baryon
                      operators. However, local multiquark operators with four or
                      more (anti)quarks are computationally expensive in this
                      framework: the cost of contractions scales with a high power
                      of the number of Laplacian eigenvectors. We present a
                      position-space sampling method within distillation that
                      reduces this cost scaling by performing the momentum
                      projection only over sparse grids rather than the full
                      spatial lattice. We demonstrate the efficiency of this
                      unbiased estimator for single-meson, single-baryon and local
                      tetraquark operators. Using Wilson-clover fermions at the
                      $SU(3)$-flavour-symmetric point, we apply this method to
                      study the importance of local tetraquark operators for the
                      finite-volume $T_{cc}(3875)^+$ spectrum. To this end, we
                      extend a large basis of bilocal $DD^*$ and $D^*D^*$
                      scattering operators by including local tetraquark
                      operators. The inclusion of local operators leads to
                      significant shifts in several energy levels. Finally, we
                      show the effect of these shifts on the $DD^*$ scattering
                      phase shift from a single-channel $s$-wave Lüscher
                      analysis.},
      cin          = {$Z_ZPPT$},
      cid          = {$I:(DE-H253)Z_ZPPT-20210408$},
      pnm          = {611 - Fundamental Particles and Forces (POF4-611) / GRK
                      2575 - GRK 2575: Überdenken der Quantenfeldtheorie
                      (417533893)},
      pid          = {G:(DE-HGF)POF4-611 / G:(GEPRIS)417533893},
      experiment   = {EXP:(DE-MLZ)NOSPEC-20140101},
      typ          = {PUB:(DE-HGF)25},
      eprint       = {2510.26459},
      howpublished = {arXiv:2510.26459},
      archivePrefix = {arXiv},
      SLACcitation = {$\%\%CITATION$ = $arXiv:2510.26459;\%\%$},
      doi          = {10.3204/PUBDB-2025-04436},
      url          = {https://bib-pubdb1.desy.de/record/639335},
}