\section{Introduction}
%\vspace{-10pt}

\label{sec:intro}
The ASU Meson Physics Group is primarily interested in determining the 
existence and properties of hadronic resonance states. I have chosen to 
focus our efforts on resonance states that involve strangeness. In particular, 
we have concentrated on the excited $\Xi$ baryons and the meson resonances
that decay $K K \pi$.

As stated in the current NSAC Long-Range Plan \cite{Geesaman:2015fha}:
``[t]he new capabilities of the 12-GeV 
era facilitate a detailed study of baryons containing two 
and three strange quarks. Knowledge of the spectrum of 
these states will further enhance our understanding of 
the manifestation of QCD in the three-quark arena.'' 
It is our goal to provide the detailed data regarding the 
excited $\Xi$ baryons.

Improving our understanding of quark confinement
in hadrons requires deepening our insight into the
gluonic fields within those particles.
Exploration of the spectrum and properties of exotic hybrid mesons
has emerged as a key path forward for exploring quark
confinement. Indeed, that topic
was a major motivation for the upgrade of JLab,
and is specifically mentioned multiple times
in the NSAC Long-Range Plan \cite{Geesaman:2015fha}.

For our study of mesonic resonances, the primary focus is to assist in fully mapping out 
the light meson nonets while pushing upwards in mass towards potential discoveries
of exotic hybrid meson states that decay $K^* \bar{K}$. 
The presence of non-standard $J^{PC}$ quantum numbers would be sufficient to
clearly identify a meson as being ``exotic''. To assist in the $J^{PC}$ determination, the 
degree of photon polarization is very useful. The
knowledge of the degree of photon polarization is required for determining beam asymmetries, which in turn, 
help establish the parity quantum number $P$.

The ASU Meson Physics Group successfully proposed, designed, built, and now operates                                          
a first-of-its-kind triplet-photoproduction photon-polarimeter (TPOL)                                                         
to measure the degree of linear polarization of the Hall D  photon beam. The group will remain responsible for 
determining the polarization of the photon beam for all experiments in Hall D. 

During the current award period, undergraduate research has been utilized to good effect.
The undergraduate participants Patrick Walker, 
Rebecca Osar and Emily Lamagna worked on CLAS12 data. Mr. Walker presented his work on analyzing $K^+ K^-$ states
at the College
of Integrative Sciences and Arts (CISA) Student Research Day~\cite{walker:CISA20} and presented an 
analysis $K^*$ $K$ final states at the ASU Undergraduate Physics Symposium~\cite{walker:PhysSymposium}, successfully defended his honors thesis, 
graduated with his B.S degree and won the ASU Department of Physics Research Award. 
Ms. Osar presented results from her event generator at the CISA Student Research Day~\cite{osar:CISA20} and her results of $K \Lambda^*$ states electropruduced from the proton at the ASU 
Undergraduate Physics Symposium~\cite{osar:PhysSymposium}. 
Ms. Lamagna is in the process of analyzing the reaction $e p \rightarrow e p \phi \pi$ and showed her work at the ASU Undergraduate Physics 
Symposium~\cite{lamagna:PhysSymposium}.
Additionally, undergraduate student Anna Costelle won the ASU Women in Physics Award for 
Undergraduate Research for her presentation describing the development of an event generator 
for strangeness states~\cite{costelle:PhysSymposium}. 
In May of 2020, undergraduate student Mohamed Mohamed won the CISA Undergraduate Research Award for his work on 
energy deposition studies using the Monte Carlo simulation software GEANT4~\cite{momo:poster1} and for 
a study on the use of decision trees to assist in particle identification~\cite{momo:poster2}. Undergraduate 
student Kevin Scheuer presented his study of machine learning methods for $K \pi$ 
at the spring 2020 CISA research symposium~\cite{kevin:poster}.

While we are very proud of our undergraduates, the primary focus of our work is accomplished by our
graduate students.
Graduate student Sebastian Cole (now Dr. Cole) 
successfully defended his dissertation that was based on 
studies utilizing AmpTools (partial wave analysis software) to find the $J=0$, $J=1$ and 
$J=2$ contributions to the mass spectrum of $K^*$ $K$ states in the mass region below 1.6 GeV.
Sebastian won the CISA outstanding graduate student award in December of 2020. 
%and I have
%nominated Dr. Cole for the Four Corners Section of the American Physical Society, Harry Lustig Award. 
Graduate student Brandon Sumner
has refined his preliminary cross sections for $\gamma p \rightarrow K^+ K^+ \Xi^-(1530)$,
where $\Xi^-(1530) \rightarrow \Xi^- \pi^0$. 
Brandon has also begun analyzing data for excited cascades to 
decay $\Xi^0 \pi^-$ as well as to $K^- \Lambda$.
Graduate student Alan Gardner just finished his first year and assisted Sebastian Cole in 
building code used in the partial wave analysis of the $K^*$ $K$ from GlueX data. 
Prior to his graduate studies, 
Alan conducted a preliminary search for the $\Xi^-$ baryon using CLAS12 data.

The Primary Investigator (PI) performed studies of systematics of the polarization measurement from the 
ASU triplet polarimeter 
associated with the converter thickness, performed final-stage analysis of polarimeter 
data for the 2020 data set (ongoing) and assisted students in analysis projects related 
to GlueX and CLAS12 data.
 

%Concerted efforts over the past several decades have helped identify
%and characterize many excited states for the lightest baryon - the nucleon -
%and for the lightest mesons. 
%The vast amount of information gleaned  for the lightest hadrons
%has led to tremendous progress in arriving at a description of
%those particles using QCD. Yet, these very same detailed measurements 
%have deepened the mystery of why such QCD-based descriptions of 
%nucleon excited states invariably predict many more states than observed---
%the so-called ``missing resonance'' problem.

%Going beyond the lightest hadrons, progress towards a clearer understanding
%of heavier hadrons containing one or more strange quarks arguably has been much slower.
%Flavor symmetry predicts a spectrum of excited states
%for heavier baryons at least as rich as that for the nucleon. 
%Furthermore, the existence of hybrid mesons are a natural extension of the
%constituent quark model when real excitations of gluonic fields are allowed.
%Naively, with the presence of one or more strange quarks, 
%one might think QCD-based descriptions for those heavier particles
%would be more straightforward, robust, and successful 
%than those currently attainable for the nucleon and the lightest mesons.
%However, comparatively very little data exists for those heavier particles, and 
%experimental evidence for predicted hybrid and other exotic meson states 
%remains tenuous and controversial.
%Major improvements in our empirical knowledge of the properties of these states   
%should lead directly to 
%advances in QCD descriptions of all hadrons,
%including better predictions for 
%the lightest particles consisting solely of up or down quarks.

This proposal seeks support for a program of measurements that will provide
improvements in our knowledge of hadron spectroscopy, 
focused on activities at Jefferson Lab (JLab) (1) within Hall B  using
the CEBAF Large Acceptance Spectrometer (CLAS) newly upgraded for                                                             
experiments using the 12 GeV beam at JLab (CLAS12)                                                                            
and (2)  within Hall D using the GlueX detector.   

We will obtain and analyze data using the GlueX and CLAS12 detectors
to explore the spectrum of multi-strange-quark baryons in order to 
assist in resolving the missing resonance problem for $\Xi$ states
and to refine our knowledge of the excited $\Xi$ properties. 
We will also map out the light mesons that decay $K K \pi$ with a
particular interest in finding meson resonances that exhibit exotic $J^{PC}$
quantum numbers.

%Two complementary approaches will be pursued:
%\begin{enumerate}
%\item Working with the CLAS Collaboration,

%\item Working with the GlueX Collaboration, 
%\end{enumerate}

%This proposal seeks support for a program of measurements that will provide
%major improvements in our knowledge of hadron spectroscopy, 
%focused on activities at Jefferson Lab (JLab) (1) within Hall B  using
%the CEBAF Large Acceptance Spectrometer (CLAS) newly upgraded for 
%experiments using the 12 GeV beam at JLab (CLAS12)
%and (2)  within Hall D using the GlueX detector.
%ASU will conduct investigations with two large international collaborations  to
%provide data which will be critical to advancing our
%understanding of  how quarks and gluons assemble into 
%mesons and baryons.
%Both the Hall B and the Hall D activities outlined below 
%seek to identify heretofore unobserved excited states of multi-quark systems and
%to clarify the properties of those states
%so that theoretical models of those multi-quark systems will be informed by
%the most accurate and complete database possible.

Currently, the ASU Meson Physics Group is comprised of the principal investigator 
Associate Professor Michael Dugger,
Graduate Research Assistant Brandon Sumner, 
Graduate Research Assistant Alan Gardner, 
senior undergraduate student Shane Watters, 
senior undergraduate student Emily Lamagna and
junior undergraduate student Rebecca Osar.
The proposal seeks 
%steady-state 
funding for supporting the
principal investigator (PI), two graduate students and to assist 
in undergraduate participation in remote meetings.

%We will obtain and analyze data using the newly-built CLAS12 detector
%to explore the spectrum of multi-strange-quark (``very strange'') baryons. ASU 
%simulations already have helped establish the initial running configuration for CLAS12, 
%and confirmed the feasibility of our experimental program. 
%Our extensive experience in meson photoproduction with CLAS during the 6 GeV era 
%and our interests in hybrid and exotic
%mesons led us to extend our program to the Hall D facilities,
%which we have helped bring to full operation, because
%those facilities were specifically tailored to carry out searches for those particles. 

%Based on our prior experience with polarized photon beams in Hall B during the 6 GeV era,
%the ASU Meson Physics Group successfully proposed, designed, built, and now operates 
%a first-of-its-kind triplet-photoproduction photon-polarimeter (TPOL)
%for the Hall D linearly-polarized photon beam. 
%The TPOL device, discussed more fully in section 2.2.2,
%precisely characterizes the degree of polarization of the photon beam in Hall D.
%Thus, beyond the fundamental physics goals of our research program described above, 
%our group will remain responsible for determining the polarization of the photon beam 
%for all experiments in Hall D.
%This contribution is critical: only precise knowledge of the Hall D photon beam can
%empower the full exploitation of Hall D's capabilities
%to probe the physics of hybrid and exotic hadrons with GlueX,
%as well as to carry out the studies proposed here. 



% Kevin took PHY499 with me during the spring 2020 semester. He presented his study of machine learning methods
%for $K \pi$ identification at the spring 2020 CISA research symposium [24].



%{\bf{2020}}
%Mohamed Mohamed (undergraduate student): He gave a presentation of his work on using decision trees to assist in particle identification during the spring 2020 CISA research symposium [20]. Mohamed won the CISA undergraduate research award in May of 2020.

%Rebecca Osar (undergraduate student): She presented her work on the creation of an event generator for the reaction $\gamma p \rightarrow p K^+ K^-$
%during the fall 2020 CISA research symposium [21].

%Patrick Walker (undergraduate student):  Patrick presented his work on the isolation of the $phi$ meson at the fall 2020 CISA research symposium [22] 
%and at a Very Strange meeting [23].

%Kevin Scheuer (undergraduate student): Kevin took PHY499 with me during the spring 2020 semester. He presented his study of machine learning methods 
%for $K \pi$ identification at the spring 2020 CISA research symposium [24]. 

%Sebastian Cole (graduate student): 
%I am the chair of his Ph.D. committee and supervised him for PHY 792. Sebastian made several presentations over the year [10-13]. 
%One of the presentations [10] discusses the creation of monitoring histograms that are used by shift takers during data acquisition 
%at Jefferson Lab in Newport News VA. Another presentation [11] discusses a simulation study for the $K^+ K^- \pi^0$ photoproduced from the proton. 
%The cross sections were shown in May [13]. Sebastian also presented results [12] at the fall 2020 CISA research symposium.  
%He won the CISA outstanding graduate student award in December of 2020.

%Brandon Sumner (graduate student):  Brandon made several presentations during the year [14-16]. He presented plans for an upgrade to the 
%ASU built triplet polarimeter [14] (project put on hold due to pandemic). Brandon showed his results for the cascade baryon $\Xi$) normalized 
%yields [15] and study of confidence level cuts [16]. 
 
%Alan Gardner (graduate student): Alan created a few presentations during the year [17-19] and provided me with correction factors for a presentation 
%I gave [8] to the Very Strange gorup. Alan presented a preliminary search for the $\Xi^-$ baryon [17], showed a scheme for kinematic binning of $\Lambda(1520)$ 
%states [18] and implementation of energy corrections with event topology study [19].

%[10] https://halldweb.jlab.org/wiki/images/a/a7/TPOL_2019_11_running.pdf TPOL results, GlueX meeting 2-4-2020
%[11] http://meson.hldsite.com/presentations/others/SEB-1-23-2020-BGGEN_Study_new.pdf Simulation study, GlueX meeting 1-23-2020
%[12] http://meson.hldsite.com/presentations/CISAFall20/SebastianCole_CISA_Fall_2020.pdf K* K in GlueX, CISA poster session for fall 2020
%[13] https://halldweb.jlab.org/wiki-private/images/b/b5/KStarK_CrossSection.pdf  K* K production cross sections, GlueX meeting 5-29-2020
%[14] https://userweb.jlab.org/~dugger/triPol/TPOLUpdate1-21-20.pdf TPOL update, GlueX meeting 1-21-2020
%[15] http://lc.asu.edu/~testUser/Hyperon5120.pdf Cascade production, GlueX meeting 5-1-2020
%[16] http://lc.asu.edu/~testUser/HyperonNew52920.pdf Cascade production, GlueX meeting 5-29-2020
%[17] http://meson.hldsite.com/presentations/others/May19_2020-Alan-Gardner.pdf Lambda and cascade searches, Very Strange meeting 5-19-2020

%%[20] http://meson.hldsite.com/presentations/Poster2020/PosterMoMoSp20Final.pdf Particle ID study, CISA poster session for spring 2020
%[21] http://meson.hldsite.com/presentations/CISAFall20/RebeccaOsar_CISA_Fall_2020.pdf Event generator for the p K+ K- events, CISA poster session for fall 2020.
%%[22] http://meson.hldsite.com/presentations/CISAFall20/PatrickWalker_CISA_Fall_2020.pdf Isolation of phi-meson states, CISA poster session fall 2020
%[23] http://meson.hldsite.com/presentations/others/veryStrange12-15-2021Walker.pdfIsolation of phi-meson states, Very Strange meeting 12-15-2021
%%[24] http://meson.hldsite.com/presentations/Poster2020/PresentationKevin2020.pdf Machine learning methods, CISA poster session for spring 2020



%{\bf{FUTURE STUFF}}



%The program outlined in the following sections, 
%will obtain precise, extensive data
%detailing the excitation spectra of two- and three-quark systems,
%including previously unobserved or poorly-measured three-quark states,
%as well as hybrid mesons.
%No comprehensive QCD-based description of how hadrons are built from quarks
%and gluons can be achieved without such information. 
%Two complementary approaches will be pursued:

%\begin{enumerate}

%\item Working with the CLAS Collaboration,
%ASU will lead an experiment with the newly-installed
%CLAS12 detector in Hall B
%to study excitations of $\Omega^-$ and $\Xi$ baryons
%using quasi-real incident photons. These data will
%produce the largest sample of
%photoproduced $\Xi$ baryons ever, elucidating the excitation spectrum for that hadron,
%and also yield the first data on
%photoproduced $\Omega^-$ baryons.
%The availability of a large sample of excited $\Xi$ states
%will allow
%measurement of poorly-known decay modes, many of which are
%currently listed simply as
%``seen'' or ``small'' within the current PDG summary \cite{Olive:2016xmw}.

%\item
%Working with the GlueX Collaboration,
%the ASU group will participate in the search 
%for exotic hadrons with masses up to $2.5$~GeV, with
%a particular emphasis on identifying the $\eta^{\prime}_1$ hybrid meson 
%to rule out potential tetra-quark states.
%Identifying such particles requires the determination of exotic
%quantum numbers $J^{PC}$ that do not correspond to those seen in the
%traditional constituent
%quark model. 
%Accurate knowledge of the energy and degree of polarization of the
%tagged photon beam is mandatory for all
%analyses in Hall D, and ASU's TPOL will provide
%direct measurements of the photon beam polarization for all experiments in Hall D.
%\end{enumerate}



%\newpage
