Jun 2 – 7, 2019
Carnegie Mellon University
America/New_York timezone

## Bootstrap-based fit of proton scalar polarizabilities to real Compton scattering data, using fixed−t subtracted dispersion relations

Jun 4, 2019, 4:30 PM
30m
Rangos 3

### Rangos 3

Electroweak Probes

### Speaker

Mr Stefano Sconfietti (Universita' degli Studi di Pavia & INFN, Pavia)

### Description

Stefano Sconfietti$^{1,2}$, Barbara Pasquini$^{1,2}$, and Paolo Pedroni$^{2}$

1: Dipartimento di Fisica, Università degli Studi di Pavia, 27100 Pavia, Italy,
2: Istituto Nazionale di Fisica Nucleare, Sezione di Pavia, 27100 Pavia, Italy

I will discuss the results of the the extraction of static scalar polarizabilities from real Compton scattering (RCS) data off the proton, obtained from a bootstrap-based fit combined with the theoretical framework of dispersion relations (DRs) [1]. Nucleon scalar polarizabilities $\alpha_{E1}$ and $\beta_{M1}$ are structure constants that parametrize the spin-independent response of the nucleon to an external quasi-static electromagnetic field.
In the framework of fixed−t subtracted DRs, the 6 functions that parametrize the RCS amplitude are obtained from dispersive integrals, with an additional subtraction constant for each function. Specific combinations of these constants are related to 6 polarizabilities: four of them are spin-dependent, the remaining two are the electric $\alpha_{E1}$ and magnetic $\beta_{M1}$ polarizabilities.
In this framework, I performed a fit of $\alpha_{E1}$ and $\beta_{M1}$ to the data of unpolarized proton RCS differential cross section, using a bootstrap-based technique. The main idea of this technique is the Monte Carlo sampling of replicas from the probability distribution of the original data. The conventional $\chi^2$ fitting strategy is recovered when only statistical errors are included in data analysis, while the inclusion of systematic sources of uncertainties modifies the limit probability distribution of the minimization function [2].
I will discuss the global fitted values of $\alpha_{E1}$ and $\beta_{M1}$ , their comparison with the previous extractions (obtained in the framework of unsubtracted DRs and chiral perturbation theory), and the statistical features of the bootstrap-based strategy.

[1] B. Pasquini, P. Pedroni and S. Sconfietti, arXiv:1903.07952.
[2] P. Pedroni and S. Sconfietti, in preparation.

Early Consideration Yes Yes

### Primary authors

Mr Stefano Sconfietti (Universita' degli Studi di Pavia & INFN, Pavia) Prof. Barbara Pasquini (Universita' degli Studi di Pavia & INFN, Pavia) Prof. Paolo Pedroni ( INFN, Pavia)