56 research outputs found
Measuring quark polarizations at ATLAS and CMS
Being able to measure the polarization of quarks produced in various
processes at the LHC would be of fundamental significance. Measuring the
polarizations of quarks produced in new physics processes, once discovered, can
provide crucial information about the new physics Lagrangian. In a series of
recent papers, we have investigated how quark polarization measurements can be
done in practice. The polarizations of heavy quarks (b and c) are expected to
be largely preserved in the lightest baryons they hadronize into, the Lambda_b
and Lambda_c, respectively. Furthermore, it is known experimentally that
s-quark polarization is preserved as well, in Lambda baryons. We study how
ATLAS and CMS can measure polarizations of b, c and s quarks using certain
decays of these baryons. We propose to use the Standard Model ttbar and Wc
samples to calibrate these measurements. We estimate that the Run 2 dataset
will suffice for measuring the quark polarizations in these Standard Model
samples with precisions of order 10%. We also propose various additional
measurements for the near and far future that would help characterize the
polarization transfer from the quarks to the baryons.Comment: 6 pages, proceedings of LFC17: Old and New Strong Interactions from
LHC to Future Colliders, Trento, September 11-15, 201
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Unparticle Example in 2D
We discuss what can be learned about unparticle physics by studying simple quantum field theories in one space and one time dimension. We argue that the exactly soluble 2D theory of a massless fermion coupled to a massive vector boson, the Sommerfield model, is an interesting analog of a Banks-Zaks model, approaching a free theory at high energies and a scale-invariant theory with nontrivial anomalous dimensions at low energies. We construct a toy standard model coupling to the fermions in the Sommerfield model and study how the transition from unparticle behavior at low energies to free particle behavior at high energies manifests itself in interactions with the toy standard model particles.Physic
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