Nuclear Theory·nucl-th

Friday·August 31, 2018

11 papers—9 primary·2 cross-listed

10
Reinterpreting the weak mixing angle from atomic parity violation in view of the Cs neutron rms radius measurement from COHERENT
Matteo Cadeddu🇮🇹 · Francesca Dordei🇮🇹
Using the model independent average neutron rms radius of $^{133} Cs$ and $^{127} I$ obtained from the analysis of the coherent elastic neutrino-nucleus scattering data of the COHERENT experiment, we remove the long-standing $1.5 σ$ tension between the Standard Model prediction and the weak mixing angle measurement from the atomic parity violation (APV) in caesium. The updated APV result becomes $sin^{2} ϑ_{W} = 0.239_{- 0.007}^{+ 0.006}$ , to be compared with the Standard Model prediction at low momentum transfer, $sin^{2} ϑ_{W}^{SM} = 0.23857 (5)$ . Moreover, exploiting the fact that the APV result is highly sensitive to the caesium neutron rms radius, $R_{n}$ , and assuming that the Standard Model is correct, we combine the APV and the COHERENT measurements in order to get a better determination of $R_{n}$ . The value of $R_{n} = 5.42 \pm 0.31 fm$ is obtained, improving significantly the current uncertainty. This result allows to infer a meaningful value of the caesium neutron skin, the difference between the neutron and proton distribution radii, equal to $Δ R_{n p} = 0.62 \pm 0.31 fm$ , showing for the first time a $2 σ$ deviation from zero.
↳ hep-phnucl-thPRD(2019)·78 citations
11
Valence Quark Transversity at Small $x$
Yuri V. Kovchegov🇺🇸 · Matthew D. Sievert🇺🇸
In our previous work we established a formalism which allows one to determine the small- $x$ asymptotics of any transverse momentum-dependent parton distribution function (TMD PDF) of the proton at small values of strong coupling. In this paper we apply this formalism to the valence quark transversity TMD. We relate the valence quark transversity to the transversely polarized dipole scattering amplitude, written in terms of the fundamental transversely-polarized "Wilson line" operator, an expression for which we derive explicitly as well. We then write down the evolution equation for the transversely polarized dipole amplitude. Solving that equation we arrive at the following small- $x$ asymptotics of the valence quark transversity in the large- $N_{c}$ limit: \begin{align} h_{1T}^v (x, k_T^2) \sim h_{1T}^{\perp \, v} (x, k_T^2) \sim \left( \frac{1}{x} \right)^{-1 + 2 \, \sqrt{\frac{\alpha_s \, N_c}{2 \, \pi}} } . \notag \end{align} This result is in agreement with one of the two possible small- $x$ asymptotics for the transverse structure function found previously by Kirschner, Mankiewicz, Schäfer, and Szymanowski.
↳ hep-phnucl-thPRD(2019)·52 citations

Affiliations

first authorsco-authorsvia INSPIRE

Reinterpreting the weak mixing angle from atomic parity violation in view of the Cs neutron rms radius measurement from COHERENT

Valence Quark Transversity at Small x

Affiliations

Valence Quark Transversity at Small $x$