#nuclear seminar

First Results from the SIDIS Program at CLAS12

Date: 
Thursday, April 15, 2021 - 2:00pm to 3:00pm
Location: 
online
Type of Event (for grouping events):

Semi-inclusive deep-inelastic scattering (SIDIS) is an essential tool to probe the quark-gluon structure of the proton and thus for our understanding of non-perturbative QCD dynamics. The CLAS12 experiment has been taking physics data at the upgraded Continuous Electron Beam Accelerator Facility (CEBAF) at Jefferson Laboratory since 2018. It takes advantage of the world record luminosities provided by CEBAF to perform an ambitious program of 3D imaging of the proton in momentum and position space. This talk will present the first results from the SIDIS program. I will focus on the first observation of beam-spin asymmetries in di-pion production in SIDIS. From the measured di-pion correlations a first extraction of the collinear twist-3 PDF e(x), which is sensitive to quark-gluon correlations in the proton, can be performed. Furthermore spin-orbit correlations in the hadronization of longitudinal polarized quarks into pions can be studied for the first time.

 
Meeting Recording:
 

Untangling the neutron’s electroweak radiative corrections

Date: 
Thursday, April 22, 2021 - 2:00pm to 3:00pm
Type of Event (for grouping events):
The success of the Standard Model of particle physics derives from its impressive capacity for calculating quantum corrections to extremely high precision. This is particularly the case for the neutron - a system which interacts strongly, weakly and electromagnetically - which is rich in physics without being prohibitively complex, making it a prime candidate for searching for Beyond Standard Model (BSM) physics. Besides top-row unitarity tests of the Cabibbo-Kobayashi-Maskawa matrix, the rise of precise lattice QCD calculations in recent years have enabled direct searches for exotic right-handed weak currents which arise naturally in many BSM scenarios. Both of these require exquisite control of electroweak radiative corrections, the latter of which has seen a surge of activity in the past three years. Recently, we have calculated for the first the complete electroweak radiative corrections to the nucleon axial charge, gA, up to next-to-leading order, indicating that experimental results for gA must be corrected for when comparing to lattice results. Additionally, differences between two main approaches for calculating corrections to the nucleon vector charge were shown to be reconcilable, confirming the tremendous physics reach of the neutron.
 
 

 

An accurate determination of the neutron skin thickness of Pb208 through parity-violation in electron scattering

Date: 
Thursday, April 1, 2021 - 2:00pm to 3:00pm
Type of Event (for grouping events):

While the proton radius of a nucleus is precisely measured by performing electron elastic scattering on the nucleus, the neutron radius previously measured by hadronic scattering experiments and other methods suffers from uncontrolled uncertainties due to hadronic dynamics. Opposite to the electromagnetic charge, the neutron has a much larger weak charge than the proton. Utilizing this, in PREX-2, we extracted the neutron radius of Pb208 by measuring the parity violating asymmetry obtained through performing longitudinal polarized electron scattering on the lead target. The heavy nuclei Pb208 shares the same equation of state with the neutron stars, even though it is 18 orders of magnitude smaller than neutron stars. The neutron skin thickness of Pb208 extracted from PREX-2 will accurately constrain the density dependence of the symmetry energy of nuclear matter near saturation density, which is important in the determination of the neutron star size. An overview of the PREX-2 experiment and its results will be presented.

 

Meeting Recording:
 

Novel Nucleon Structure with Transverse Polarization

Date: 
Thursday, March 4, 2021 - 2:00pm to 3:00pm
Type of Event (for grouping events):
Abstract: In this talk, we will present our recent research on transverse spin physics, focusing on two topics: (1) transverse spin sum rule; (2) single transverse spin asymmetries in dijet production at RHIC. 
 
Meeting Recording:
 

Nucleon and nuclear structure from measurements in muonic and normal atoms

Date: 
Thursday, March 11, 2021 - 2:00pm to 3:00pm
Location: 
online
Type of Event (for grouping events):

Laser spectroscopy of simple atoms is sensitive to properties of the atomic
nucleus, such as its charge and magnetization distribution, or its
polarizability. This allows determining the nuclear parameters from atomic
spectroscopy, but also limits the attainable precision for the determination of
fundamental constants or the test of QED and the Standard Model.

In light muonic atoms and ions, one negative muon replaces all atomic electrons,
resulting in a calculable hydrogen-like system. Due to the muon's large mass
(200 times the electron mass), the muon orbits the nucleus on a 200 times
smaller Bohr radius, increasing the sensitivity of muonic atoms to nuclear
properties by 200^3 = 10 million.

This has resulted in a 10fold increase in the precision of the charge radius of
the proton, deuteron, and the stable helium nuclei. The consequences for atomic
and nuclear physics, the determination of fundamental constants, and the test of
QED and the Standard Model are discussed.

 

https://www.dropbox.com/sh/69sdbudfg8245pj/AACTb2WyBF_R2ujBHJkIx6zja?dl=0

Meeting Recording:
 
 

First-principles calculation of the nucleon axial charge

Date: 
Thursday, February 11, 2021 - 2:00pm to 3:00pm
Type of Event (for grouping events):
Understanding theoretically the neutrino-nucleus cross section is critical to the success of future neutrino oscillation experiments such as DUNE and Hyper-K. For neutrino energy at around 1 GeV, the nucleon axial form factor limits the precision of the cross section model as it is difficulty to measure experimentally. In this talk, I will discuss how lattice QCD can provide first-principles calculations of nucleon matrix elements. In particular, I will focus on the first calculation of the nucleon axial charge, the nucleon axial form factor at zero momentum transfer, with an efficient lattice fermion discretization, and discuss prospects in extending our work to the full momentum dependence.
 
 
 
 
 
 
 
 
 

 

Radiative corrections in neutrino scattering

Date: 
Thursday, March 25, 2021 - 2:00pm to 3:00pm
Location: 
online
Type of Event (for grouping events):
Neutrino physics is entering a precision era that requires a careful treatment of percent-level effects. In this talk, I am going to discuss the role of radiative corrections in modern and future experiments with artificial neutrino sources.
 
One-loop radiative corrections introduce the flavor dependence in the coherent elastic neutrino-nucleus scattering at the percent level. To consistently account for radiative corrections, we start from the effective field theory of neutrino-lepton and neutrino-quark interactions, embed quarks into nucleons and nucleons into nuclei. We present cross sections at energies below 100 MeV and provide a complete error budget accounting for all uncertainties at nuclear, nucleon, hadronic, and quark levels.
 
Precise knowledge of neutrino-nucleon charged-current quasielastic scattering is crucial for successful measurements of neutrino oscillation parameters at accelerator-based facilities. Exploiting effective field theory, we factorize neutrino-nucleon quasielastic cross sections into soft, collinear, and hard contributions. We evaluate soft and collinear functions from QED and provide a model for the hard contribution. Performing resummation, we account for logarithmically-enhanced higher-order corrections of percent level and evaluate precise cross sections quantifying the resulting error. We discuss the relevance of radiative corrections depending on conditions of accelerator-based neutrino experiments.
 
 

 

Skipper-CCDs for dark matter, neutrinos, quantum science and astronomy

Date: 
Thursday, February 18, 2021 - 2:00pm to 3:00pm
Type of Event (for grouping events):

The recently demonstrated skipper-CCDs have the ability to count single electronic with minimal noise.  I will discuss the current status of the electron counting skipper-CCD technology, and its applications.  Including low threshold experiments for dark matter and neutrinos, photon starved imaging in QIS and astronomy and more. I will also discuss the challenges and ongoing R&D effort for developments of the next generation experiments using this technology.

 
Meeting Recording:
 

Dark matter at the high mass frontier

Date: 
Thursday, April 8, 2021 - 2:00pm to 3:00pm
Location: 
Online
Type of Event (for grouping events):

As the search for dark matter continues, a growing number of theories predict that dark matter is a supermassive particle or composite state. Discovering dark matter at this high mass extreme requires new approaches. I will survey some recent developments, including dark matter that forms black holes in the sun and earth, dark matter that would make old white dwarfs explode, and supermassive dark matter detected through its fusion of nuclei in Antarctic ice.

 
Meeting Recording:
 

Experimental Opportunities for Measuring Neutrino Nucleon Scattering with H$_2$/D$_2$ Detectors

Date: 
Thursday, February 25, 2021 - 2:00pm to 3:00pm
Location: 
online
Type of Event (for grouping events):

 

Many models of neutrino-nucleus scattering are guided by data taken during the 1970's and 1980's by the Argonne, Brookhaven, and Fermilab bubble-chamber experiments, which have limited data sample sizes and large systematic uncertainties.  The long-baseline neutrino facility (LBNF) will provide a neutrino beam, primarily composed of $\nu_\mu$ when it runs with forward horn current, and $\bar\nu_\mu$ when it runs with reverse horn current.  The beam intensity is driven by the power of the proton beam on the target, which is slated to start at 1.2 MW and will be upgraded to 2.4 MW.  The near detectors currently being designed are optimized for DUNE's determination of the neutrino mass ordering and the measurement of $\delta_{\rm{CP}}$.  This powerful beam provides unprecedented opportunities to measure the cross sections of neutrinos on protons and neutrons via hydrogen/deuterium targets with integrated particle detection capability.  Options range from using the hydrogen in the scintillating plastic in the SAND near detector component, to adding hydrogen-rich gas to the high-pressure gas TPC near detector component, to building a H$_2$/D$_2$ bubble chamber in a separate hall upstream of the DUNE near detector hall. Polarized targets are also under consideration, though these will necessarily involve other elements along with the hydrogen and deuterium, but they will allow the first measurements of neutrino scattering on polarized nuclei.

https://www.dropbox.com/sh/z67mq9zfdwm6wj8/AAC2v83jGvFJOujFrVi2Nmr2a?dl=0

 
Meeting Recording:
 

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