arXiv subjects

Frank Nerling

Publications and source records attributed to Frank Nerling.

15 recordsLinked to original sources

arXiv2022

50 Years of Quantum Chromodynamics

This paper presents a comprehensive review of both the theory and experimental successes of Quantum Chromodynamics, starting with its emergence as a well defined theory in 1972-73 and following developments and results up to the present day. Topics include a review of the earliest theoretical and experimental foundations; the fundamental constants of QCD; an introductory discussion of lattice QCD, the only known method for obtaining exact predictions from QCD; methods for approximating QCD, with special focus on effective field theories; QCD under extreme conditions; measurements and predictions of meson and baryon states; a special discussion of the structure of the nucleon; techniques for study of QCD at high energy, including treatment of jets and showers; measurements at colliders; weak decays and quark mixing; and a section on the future, which discusses new experimental facilities or upgrades currently funded. The paper is intended to provide a broad background for Ph.D. students and postdocs starting their career. Some contributions include personal accounts of how the ideas or experiments were developed.

hep-ph↗

arXiv2021

Strange Hadron Spectroscopy with Secondary KL Beam in Hall D

We propose to create a secondary beam of neutral kaons in Hall D at Jefferson Lab to be used with the GlueX experimental setup for strange hadron spectroscopy. The superior CEBAF electron beam will enable a flux on the order of $1\times 10^4~K_L/sec$, which exceeds the flux of that previously attained at SLAC by three orders of magnitude. The use of a deuteron target will provide first measurements ever with neutral kaons on neutrons. The experiment will measure both differential cross sections and self-analyzed polarizations of the produced $Λ$, $Σ$, $Ξ$, and $Ω$ hyperons using the GlueX detector at the Jefferson Lab Hall D. The measurements will span CM $\cosθ$ from $-0.95$ to 0.95 in the range W = 1490 MeV to 2500 MeV. The new data will significantly constrain the partial wave analyses and reduce model-dependent uncertainties in the extraction of the properties and pole positions of the strange hyperon resonances, and establish the orbitally excited multiplets in the spectra of the $Ξ$ and $Ω$ hyperons. Comparison with the corresponding multiplets in the spectra of the charm and bottom hyperons will provide insight into he accuracy of QCD-based calculations over a large range of masses. The proposed facility will have a defining impact in the strange meson sector through measurements of the final state $Kπ$ system up to 2 GeV invariant mass. This will allow the determination of pole positions and widths of all relevant $K^\ast(Kπ)$ $S$-,$P$-,$D$-,$F$-, and $G$-wave resonances, settle the question of the existence or nonexistence of scalar meson $κ/K_0^\ast(700)$ and improve the constrains on their pole parameters. Subsequently improving our knowledge of the low-lying scalar nonet in general.

nucl-ex↗

arXiv2018

Recent results on charmonium-like (exotic) XYZ states at the BESIII/BEPCII experiment in Beijing/China

With about 12 fb$^{-1}$ collected XYZ data sets, BESIII continues the exploration of the exotic charmonium-like states. In this talk, recent results on the measurements of the spin-parity determination of $Z_{\rm c}(3900)$, as well as on line-shapes of $e^+e^- \rightarrow J/ψ\,ππ, h_{\rm c}ππ, ψ(2S)\,π^0π^0/π^+π^-$, and $π^+ D^0 D^{*-}$ from open charm are discussed. Also, the recent observation of $e^+ e^- \rightarrow ϕχ_{c1/2}$ at $\sqrt(s)=4.6$ GeV is reported.

hep-ex↗

arXiv2018

Newest results on XYZ states at BESIII

The BESIII experiment at BEPCII at IHEP in Beijing/China has collected the world largest data sets in the $τ$-charm region and it is well suited to cover a rich hadron physics programme, including charmonium and open-charm spectroscopy, $R$-scan or electromagnetic form factor measurements, and many more. In particular, the unique data sets between 3.8 and 4.6\,GeV allow for discoveries and precision measurements of the interesting charmonium-like (exotic) `XYZ' states. The recently published precision cross-section measurement for $Y$ states is discussed as well as the first observation of the $X(3872)$ in radiative decays, also the completion of the two observed isospin triplets $Z_{\rm c}(3900)$ and $Z_{\rm c}(4020)$ is briefly summarised.

hep-ex↗

arXiv2016

Highlights from the COMPASS experiment at CERN -- Hadron spectroscopy and excitations

The COMPASS experiment at the CERN-SPS studies the spectrum and the structure of hadrons by scattering high energy hadrons and polarised muons off various fixed targets. Recent results for the hadron programme comprise highlights from different topics. A selective overview is given and, among others, the following results are discussed. The precise determination of the pion polarisability, a long standing puzzle that has been solved now, is presented as well as measurements of radiative widths. The observation of a new narrow axial-vector state, the $a_1(1420)$, as well as deeper insights into the exotic $1^{-+}$-wave, which is under study since decades by several experiments, are discussed and further, the search for the charmonium-like exotic $Z_c(3900)$ state in the COMPASS data is covered.

hep-ex↗

arXiv2012

Hadron Spectroscopy with COMPASS -- Newest Results

The COMPASS experiment at the CERN SPS investigates the structure and spectrum of hadrons by scattering high energetic hadrons and polarised muons off various fixed targets. During the years 2002-2007, COMPASS focused on nucleon spin physics using 160 GeV/c polarised $μ^+$ beams on polarised deuteron and proton targets, including measurements of the gluon contribution to the nucleon spin using longitudinal target polarisation as well as studies of transverse spin effects in the nucleon on a transversely polarised target. One major goal of the physics programme using hadron beams is the search for new states, in particular the search for $J^{PC}$ exotic states and glue-balls. COMPASS measures not only charged but also neutral final-state particles, allowing for investigation of new objects in different reactions and decay channels. In addition COMPASS can measure low-energy QCD constants like, e.g. the electromagnetic polarisability of the pion. Apart from a few days pilot run data taken in 2004 with a 190 GeV/c $π^{-}$ beam on a Pb target, showing a significant spin-exotic $J^{PC}$ = $1^{-+}$ resonance at around 1660 MeV/$c^{2}$, COMPASS collected high statistics with negative and positive 190 GeV/$c$ hadron beams on a proton (H$_2$) and nuclear (Ni, Pb) targets in 2008 and 2009. We give a selected overview of the newest results and discuss the status of various ongoing analyses.

hep-ex↗

arXiv2012

Observation of a $J^{PC}=1^{-+}$ exotic signal in the $π^{-}π^{0}π^{0}$ system diffractively produced at COMPASS, and comparison to the charged decay mode

The COMPASS experiment at the CERN SPS features good charged particle tracking and coverage by electromagnetic calorimetry, and our data provide excellent opportunity for simultaneous observation of new states in two different decay modes within the same experiment. The existence of the spin-exotic $π_1(1600)$ resonance in the $ρπ$ decay channel is studied for the first time in COMPASS in both decay modes of the diffractively produced $(3π)^{-}$ system: $π^{-}p \rightarrow π^{-}π^{0}π^{0}p$ and $π^{-}p \rightarrow π^{-}π^{+}π^{-}p$. A preliminary partial-wave analysis (PWA) performed on the 2008 proton target data allows for a first conclusive comparison of both $(3π)^{-}$ decay modes not only for main waves but also for small ones, including the spin-exotic $1^{-+}$ wave. We find the neutral versus charged mode results in good agreement with expectations from isospin symmetry. Both, the intensities and the relative phases to well-known resonances, are consistent for the neutral and the charged decay modes of the $(3π)^{-}$ system. The status on the search for the spin-exotic $π_1(1600)$ resonance produced on a proton target is discussed.

hep-ex↗

arXiv2011

New results on the search for spin-exotic mesons with COMPASS

The COMPASS fixed-target experiment at the CERN-SPS studies the structure and spectrum of hadrons. One important goal using hadron beams is the search for new states, in particular spin-exotic mesons and glueballs. As a first input to the puzzle, COMPASS observed a significant $J^{PC}$ spin-exotic signal in the 2004 pilot run data (190\,GeV/$c$ $π^{-}$ beam, Pb target) in three charged pion final states consistent with the disputed $π_1(1600)$. We started our hadron spectroscopy programme in 2008 by collecting very high statistics using a 190 GeV/$c$ negative pion beam scattered off a liquid hydrogen (proton) target. The current status and new results from the 2008 data on the search for the $π_1(1600)$ resonance with exotic $J^{PC}=1^{-+}$ quantum numbers obtained from partial-wave analyses of the $ρπ$ and $η'π$ decay channels are presented.

hep-ex↗

arXiv2011

Diffractive dissociation into $K_sK^{\pm}π^{\mp}π^{-}$ final states

The COMPASS fixed-target experiment at CERN/SPS is dedicated to the study of hadron structure and spectroscopy, especially the search for spin-exotic states. After having started to study the existence of the spin-exotic $π_1(1600)$ resonance in the 2004 pilot-run data, the new 2008/09 data will enable us to further clarify the situation. Apart from the $π_1(1600)$ resonance, also a spin-exotic $π_1(2000)$ was reported in the past in the $f_1(1285)π$ decay channel by the E852/BNL experiment, however, this state still lacks confirmation. We present a first event selection of the diffractively produced $(K\bar{K}ππ)^{-}$ system showing clean $f_1(1285)$ and $f_1(1420)$ resonances at competing statistics. A partial-wave analysis started on $f_1(1285)π$ and $f_1(1420)π$ decay channels will further complete the search for spin-exotics in the 2008/09 COMPASS data.

hep-ex↗

arXiv2011

Spin-exotic search in the $ρπ$ decay channel: New results on $π^{-}π^{0}π^{0}$ in comparison to $π^{-}π^{+}π^{-}$ final states (diffractively produced on proton)

The COMPASS experiment at CERN SPS features charged particle tracking as well as good coverage by electromagnetic calorimetry, and our data provide an excellent opportunity for simultaneous observation of new states in different decay modes by the same experiment. The existence of the spin-exotic $π_1(1600)$ resonance in the $ρπ$ decay channel is studied for the first time at COMPASS in both decay modes of the diffractively produced $(3π)^{-}$ system: $π^{-}p \rightarrow π^{-}π^{+}π^{-}p$ and $π^{-} p \rightarrow π^{-}π^{0}π^{0} p$. A preliminary partial-wave analysis performed on the 2008 proton target data allows for a first conclusive comparison of both $(3π)^{-}$ decay modes not only for main waves but also for small ones. We find the neutral versus charged mode results in excellent agreement with expectations from isospin symmetry. Both, the intensities and the relative phases to well-known resonances, are consistent for the neutral and the charged decay modes of the $(3π)^{-}$ system. The status on the search for the spin-exotic $π_1(1600)$ resonance produced on a proton target is discussed.

hep-ex↗

arXiv2010

First Results on Hadron Spectroscopy at COMPASS

The COMPASS fixed-target experiment at the CERN SPS is dedicated to the study of hadron structure and dynamics. One goal of the physics programme using hadron beams is the search for new states, in particular the search for $J^{PC}$ exotic states and glueballs. After a short pilot run in 2004 (190 GeV/c $π^{-}$ beam, lead target), we started our hadron spectroscopy programme in 2008 by collecting unprecedented statistics using 190 GeV/c negative hadron beams on a liquid hydrogen target. A similar amount of data with 190 GeV/c positive hadron beams has been taken in 2009, as well as some data (negative beam) on nuclear targets. As a first result the observation of a significant $J^{PC}$ spin-exotic signal in the 2004 data -- consistent with the disputed $π_1(1600)$ -- was recently published. Our spectrometer features good coverage by electromagnetic calorimetry, crucial for the detection of final states involving $π^0$, $η$ or $η'$, and the 2008/09 data provide an excellent opportunity for the simultaneous observation of new states in different decay modes. The diffractively produced $(3π)^{-}$ system for example can be studied in $π^{-}π^{+}π^{-}$ and $π^{-}π^{0}π^{0}$ final states, respectively. Observation of new states in both modes provides important consistency checks within the same experiment as the reconstruction of charged and neutral modes rely on completely different parts of the apparatus. We present the first results and give an overview of the status on various ongoing analyses of the 2008/09 data.

hep-ex↗

arXiv2010

Meson spectroscopy with COMPASS

The COMPASS fixed-target experiment at CERN SPS is dedicated to the study of hadron structure and dynamics. In the physics programme using hadron beams, the focus is on the detection of new states, in particular the search for $J^{PC}$ exotic states and glueballs. After a short pilot run in 2004 (190 GeV/c negative pion beam, lead target), we started our hadron spectroscopy programme in 2008 by collecting an unprecedented statistics with a negative hadron beam (190 GeV/c) on a liquid hydrogen target. A similar amount of data with positive hadron beam (190 GeV/c) has been taken in 2009, as well as some additional data with negative beam on nuclear targets. The spectrometer features a large angular acceptance and high momentum resolution and also good coverage by electromagnetic calorimetry, crucial for the detection of final states involving $π^0$ or $η$. A first important result is the observation of a significant $J^{PC}$ spin exotic signal consistent with the disputed $π_1(1600)$ in the pilot run data. This result was recently published. We present an overview of the status of various ongoing analyses on the 2008/09 data.

hep-ex↗

arXiv2010

COMPASS Hadron Spectroscopy -- Final states involving neutrals and kaons

The COMPASS experiment at CERN is well designed for light-hadron spectroscopy with emphasis on the detection of new states, in particular the search for $J^{PC}$-exotic states and glueballs. We have collected data with 190 GeV/c charged hadron beams on a liquid hydrogen and nuclear targets in 2008/09. The spectrometer features good coverage by electromagnetic calorimetry and a RICH detector further provides $π$ / $K$ separation, allowing for studying final states involving neutral particles like $π^0$ or $η$ as well as hidden strangeness, respectively. We discuss the status of ongoing analyses with specific focus on diffractively produced $(π^0π^0π)^{-}$ as well as $(K\bar{K}π)^{-}$ final states.

hep-ex↗

arXiv2010

Hadron spectroscopy with COMPASS -- First results

The COMPASS experiment at CERN is dedicated to light hadron spectroscopy with emphasis on the detection of new states, in particular the search for spin exotic states and glueballs. After a short pilot run in 2004 (190 GeV/c $π^{-}$ beam, Pb target) showing significant production strength of an exotic $J^{PC}=1^{-+}$ state at 1.66\,GeV/${\rm c^2}$, we have collected data with 190 GeV/c hadron beams on a liquid hydrogen target in 2008/09. The spectrometer features good coverage by calorimetry and our data provide excellent opportunity for simultaneous observation of new states in different decay modes. The diffractively produced $(3π)^{-}$ system for example can be studied in both modes $π^{-}p \rightarrow π^{-}π^{+}π^{-}p$ and $π^{-}~p \rightarrow π^{-}π^{0}π^{0}~p$. Reconstruction of charged and neutral mode rely on completely different parts of the apparatus. Observation of new st ates in both modes provides important checks. The results on diffractive dissociation into 3$π$ final states from the 2004 data recently published are discussed as well as the first comparison of neutral vs. charged mode based on a first partial wave analysis of 2008 data.

hep-ex↗

arXiv2010

Diffractive pion production at COMPASS -- First results on 3$π$ final states - neutral mode

The COMPASS experiment at CERN is designed for light hadron spectroscopy with emphasis on the detection of new states, in particular the search for exotic states and glue-balls. After a short pilot run in 2004 (190 GeV/c negative pion beam, lead target) showing significant production strength for an exotic $J^{PC}=1^{-+}$ state at 1.66\,GeV/${\rm c^2}$, we have collected data with a 190 GeV/c negative charged hadron beam on a proton (liquid hydrogen) and nuclear targets in 2008 and 2009. The spectrometer features good coverage by electromagnetic calorimetry, and our data provide excellent opportunity for simultaneous observation of new states in two different decay modes in the same experiment. The diffractively produced $(3π)^{-}$ system for example can be studied in both modes $π^{-}p \rightarrow π^{-}π^{+}π^{-}p$ and $π^{-}~p \rightarrow π^{-}π^{0}π^{0}~p$. Charged and neutral mode rely on completely different parts of the spectrometer. Observing a new state in both modes provides important cross-check. First results of a preliminary PWA performed on the 2008 data are presented.

hep-ex↗