协变手性理论下中微子诱导的核子中性电流π0产生：非共振效应研究

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本文主要探讨了协变手性扰动理论（Covariant Chiral Perturbation Theory, CCPT）在核子产生中性电流弱介子过程中的应用，特别是在涉及中微子（ν）和反中微子（ν̅）与核子目标相互作用时的中性电流单粒子π0产生的现象。研究的焦点是显性的Δ(1232)自由度，在这种理论框架下，其贡献被量化到O(p3)阶次，即在能量尺度上对应于pion的三个质量的立方。在相对论重子手性扰动理论中，作者De-Liang Yao、Luis Alvarez-Ruso和M.J. Vicente Vacas针对低能条件下的反应，发现不同反应通道的总截面呈现出显著的非共振效应。传统的中微子振荡和截面实验，如GENIE和NuWro，通常依赖于简化模型，可能忽略了这类重要的非共振效应。CCPT的运用使得研究者能够更准确地预测这些过程在实际能量范围内的行为，这对于理解和解释中微子物理学实验数据至关重要。文章的接收日期为2019年1月9日，经过修订后于同年5月25日接受，并于5月28日在线发布。编辑A.Ringwald对本文进行了审阅。这篇工作对于深化我们对中微子与核子相互作用的理解，尤其是在低能区域的精细结构和非线性效应方面，具有重要的理论贡献。本文的核心知识点包括： 1. 协变手性扰动理论的原理与应用：在处理高能物理过程中，如何结合相对论和量子场论，构建一个适用于中子和质子相互作用的理论框架。 2. Δ(1232)自由度的作用：这个共振态在中性电流弱介子生产中的关键角色，以及它在低能区的O(p3)阶次修正。 3. 非共振效应的发现：在CCPT的计算下，如何揭示了中微子与核子相互作用中的非共振截面贡献，这对现有实验结果的修正和新实验设计有指导意义。 4. 实验应用的扩展：论文提出的结果如何影响了如GENIE和NuWro这样的中微子实验，强调了理论在现代实验物理学中的实用价值。通过阅读这篇文章，研究者可以了解到如何将理论计算与实验观察相结合，从而提高我们对基本粒子相互作用过程的精确理解和预测能力。

Physics Letters B 794 (2019) 109–113

Contents lists available at ScienceDirect

Physics Letters B

www.elsevier.com/locate/physletb

Neutral-current weak pion production off the nucleon in covariant

chiral perturbation theory

De-Liang Yao

a,b,∗

, Luis Alvarez-Ruso

, M.J. Vicente Vacas

School of Physics and Electronics, Hunan University, Changsha 410082, China

Departamento de Física Teórica and Instituto de Física Corpuscular (IFIC), Centro Mixto CSIC-UV, Institutos de Investigación de Paterna, E-46071, Valencia, Spain

a r t i c l e i n f o a b s t r a c t

Article history:

Received

9 January 2019

Received

in revised form 23 May 2019

Accepted

25 May 2019

Available

online 28 May 2019

Editor: A.

Ringwald

Neutral current single pion production induced by neutrinos and antineutrinos on nucleon targets has

been investigated in manifestly relativistic baryon chiral perturbation theory with explicit (1232)

degrees of freedom up to O(p

). At low energies, where chiral perturbation theory is applicable, the

total cross sections for the different reaction channels exhibit a sizable non-resonant contribution, which

is not present in event generators of broad use in neutrino oscillation and cross section experiments such

as GENIE and NuWro.

(http://creativecommons.org/licenses/by/4.0/). Funded by SCOAP

1. Introduction

In recent years, more precise measurements of neutrino cross

sections have been achieved, and more experiments are still ongo-

ing

or planned to enrich the wealth of data for a better determina-

tion

of the mechanisms of neutrino interactions with matter (see

for instance Ref. Mahn et al. [1] and references therein). A better

understanding of neutrino interactions with nucleons and nuclei is

of particular importance to achieve the precision goals of modern

neutrino-oscillation experiments [2,3].

Neutrino- and

antineutrino-induced single pion production are

among the dominant contributions to the inclusive (anti)neutrino-

nucleus

cross section in the relevant energy regime of several ex-

periments.

In particular, neutral current (NC) π

production can

mimic the electron-like signal in ν

→ ν

(

→

) measure-

ments.

Currently, uncertainties at the 20 − 30% level have to be

considered for single pion production in the analyses of oscillation

experiments, owing to the conﬂict between data sets and mod-

els [4].

Single pion production off the nucleon, as a fundamental

ingredient of the corresponding process on nuclei should be inves-

tigated.

Weak

single pion production off the nucleon has been exten-

sively

studied at intermediate energies with various phenomeno-

logical

models. Models accounting for the (1232) resonance and

Corresponding author.

E-mail

addresses: yaodeliang@hnu.edu.cn (D.-L. Yao), Luis.Alvarez@iﬁc.uv.es

(L. Alvarez-Ruso),

Manuel.J.Vicente@iﬁc.uv.es (M.J. Vicente Vacas).

higher nucleon excitations have been developed [5–20], with some

studies speciﬁcally addressing the NC case [21,22]. In addition to

nucleon excitation, most of these models incorporate non-resonant

amplitudes with form factors in the vertices.

Recently,

a well founded low-energy model for charged-current

(CC) weak single pion production off the nucleon has been devel-

oped

in Ref. [23]on the basis of covariant baryon chiral perturba-

tion

theory (ChPT) [24–28]. The study has been systematically per-

formed

up to chiral order O(p

), where loop diagrams are present.

The extended-on-mass-shell (EOMS) scheme [29]was adopted to

remedy the power counting breaking of ChPT in the presence of

baryons [30]. The EOMS scheme has been extensively used in var-

ious

studies of baryonic phenomenology, see e.g. Refs. [31–38],

even beyond the low-energy region [39].

Furthermore, the  res-

onance

was explicitly included according to the δ-counting rule

from Ref. [43].

this letter, we extend the study to the neutral-current reac-

tions.

For this purpose, new isoscalar amplitudes, not present in

the CC case and involving three distinctive low-energy constants

(LECs), need to be computed. Following a general description of

the electroweak amplitude for NC weak pion production on the

nucleon, the external currents and the relevant terms of the chiral

Lagrangian are introduced. The calculation of the hadronic matrix

elements is then brieﬂy described. Numerical results for integrated

The heavy-baryon approach has also proved to be adequate for pion produc-

tion

off the nucleon induced by vector, see, e.g., Refs. [40,41], and also axial [23,42]

currents,

at least very close to threshold.

https://doi.org/10.1016/j.physletb.2019.05.036

0370-2693/

SCOAP

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