Proton Size Anomaly

Barger, V.; Chiang, Cheng‐Wei; Keung, Wai-Yee; Marfatia, Danny

doi:10.1103/physrevlett.106.153001

Cited by 134 publications

(145 citation statements)

References 39 publications

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“…Further noted in [7], neutron scattering constraints only limit models with very light new particle masses (under 5 MeV), other muonic atom energy splittings give bounds already below ones discussed, the π → γV decay where V is a massive vector only impacts an m V mass range that is already excluded, and the limits from nonobservance of the decay η → V V is not serious for m V below m η /2 given the results in Figs. 1 and 2.…”

Section: Closing Commentsmentioning

confidence: 89%

“…They showed that in first order of nonrelativistic perturbation theory, exchange particle masses of order MeV could produce the observed Lamb shift, albeit exchanges with masses this light run afoul of neutron scattering data if the neutron and proton have similar coupling. Barger et al [7] also considered new scalar and vector particles, but suggested it would be difficult for them to satisfy additional constraints placed by Υ, J/ψ, π, and η-decays.…”

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confidence: 99%

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New physics and the proton radius problem

2012

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Background: The recent disagreement between the proton charge radius extracted from Lamb shift measurements of muonic and electronic hydrogen invites speculation that new physics may be to blame. Several proposals have been made for new particles that account for both the Lamb shift and the muon anomalous moment discrepancies. Purpose: We explore the possibility that new particles' couplings to the muon can be fine-tuned to account for all experimental constraints. Method: We consider two fine-tuned models, the first involving new particles with scalar and pseudoscalar couplings, and the second involving new particles with vector and axial couplings. The couplings are constrained by the Lamb shift and muon magnetic moments measurements while mass constraints are obtained by kaon decay rate data. Results: For the scalar-pseudoscalar model, masses between 100 to 200 MeV are not allowed. For the vector model, masses below about 200 MeV are not allowed. The strength of the couplings for both models approach that of electrodynamics for particle masses of about 2 GeV. Conclusions: New physics with fine tuned couplings may be entertained as a possible explanation for the Lamb shift discrepancy.

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Section: Closing Commentsmentioning

confidence: 89%

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confidence: 99%

New physics and the proton radius problem

2012

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“…A fairly obvious use for contact interactions in the point-particle action is to parametrize the effects of any hypothetical new forces acting between nuclei and electrons or muons, and in particular forces that differ in strength between these two (since these can be captured through species-dependent values for c s and c v , unlike for r p ). Indeed the observation that the existence of such short-range interactions could, in principle, explain the proton radius puzzle [38][39][40] has led to efforts to better understand their size [53] and to the proposal of exotic interactions of this type [62][63][64][65].…”

Section: Jhep09(2017)007mentioning

confidence: 99%

Point-particle effective field theory III: relativistic fermions and the Dirac equation

Burgess¹,

Hayman²,

Rummel³

et al. 2017

J. High Energ. Phys.

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We formulate point-particle effective field theory (PPEFT) for relativistic spinhalf fermions interacting with a massive, charged finite-sized source using a first-quantized effective field theory for the heavy compact object and a second-quantized language for the lighter fermion with which it interacts. This description shows how to determine the near-source boundary condition for the Dirac field in terms of the relevant physical properties of the source, and reduces to the standard choices in the limit of a point source. Using a first-quantized effective description is appropriate when the compact object is sufficiently heavy, and is simpler than (though equivalent to) the effective theory that treats the compact source in a second-quantized way. As an application we use the PPEFT to parameterize the leading energy shift for the bound energy levels due to finite-sized source effects in a model-independent way, allowing these effects to be fit in precision measurements. Besides capturing finite-source-size effects, the PPEFT treatment also efficiently captures how other short-distance source interactions can shift bound-state energy levels, such as due to vacuum polarization (through the Uehling potential) or strong interactions for Coulomb bound states of hadrons, or any hypothetical new short-range forces sourced by nuclei.

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“…The perhaps most tantalizing deviation occurs in the ratio R K = B(B + → K + µ + µ − )/B(B + → K + e + e − ), which was observed about 2.6 σ below the theoretically clean SM prediction, 1 We do not consider the proton size anomaly observed in muonic hydrogen atoms [6]. NP interpretations of this measurement are very challenging [7,8].…”

Section: Introductionmentioning

confidence: 99%

Dark matter relic from muon anomalies

2015

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We show that the recently reported anomalies in b → sµ + µ − transitions, as well as the longstanding gµ − 2 discrepancy, can be addressed simultaneously by a new massive abelian gauge boson with loop-induced coupling to muons. Such a scenario typically leads to a stable dark matter candidate with a thermal relic density close to the observed value. Dark matter in our model couples dominantly to leptons, hence signals in direct detection experiments lie well below the current sensitivity. The LHC, in combination with indirect detection searches, can test this scenario through distinctive signatures with muon pairs and missing energy.

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Proton Size Anomaly

Cited by 134 publications

References 39 publications

New physics and the proton radius problem

New physics and the proton radius problem

Point-particle effective field theory III: relativistic fermions and the Dirac equation

Dark matter relic from muon anomalies

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