scholarly journals Beam Asymmetries from Light Scalar Meson Production on the Proton at GlueX

2020 ◽  
Vol 1643 (1) ◽  
pp. 012169
Author(s):  
Stuart Fegan
Keyword(s):  
Scalar Meson ◽  
Meson Production ◽  
Real Photon ◽  
Final States ◽  
Ongoing Research ◽  
Beam Asymmetry ◽  
Strong Force ◽  
Beam Asymmetries ◽  
Light Scalar ◽  
Large Acceptance

Abstract The GlueX facility, featuring a linearly polarised 9 GeV real photon beam delivered to a large-acceptance detector system, has recently completed its first phase of running, and analysis efforts of this dataset are well underway. It has been suggested that at GlueX energies, quark systems beyond the three quark and quark-antiquark systems of baryons and mesons, such as hybrid mesons, tetraquarks and glueballs, should exist, and studies of these systems could shed new light on how quarks combine under the strong force, particularly the role played by gluons. Meticulous study of the spectrum of hadronic states is required to understand the strong force in the non-perturbative energy regime, and the light scalar meson sector is an area that remains poorly understood. GlueX data encompasses final states at energies where photoproduction of the a0 (980) and f 0 (980) mesons can provide discriminatory evidence between various models, manifested in experimental observables such as the cross section and beam asymmetry, and performing detailed measurements of these quantities is considered a priority of the ongoing research program. The work presented showcases efforts to measure the beam asymmetry of the reaction γp→pηπ whose mass spectrum encompasses several mesons, including the a 0(980) light scalar, and the a 2(1320) tensor. Future prospects for related analyses in the light scalar meson sector, informed by this measurement, will also be discussed.

scholarly journals Spin Physics with Photons — Technical Highlights and Spin-Offs

2016 ◽  
Vol 40 ◽  
pp. 1660064
Author(s):  
A. Thomas
Keyword(s):  
Nuclear Physics ◽  
Superconducting Magnets ◽  
Fundamental Property ◽  
Real Photon ◽  
Final States ◽  
Polarized Beams ◽  
Polarized Target ◽  
Angular Acceptance ◽  
Spin Polarized ◽  
Large Acceptance

The spin, as a fundamental property of a particle, has been a main object of investigation in particle and nuclear physics research in recent decades. For complete spin investigation, one requires a polarized target in addition to polarized beams and a recoil polarimeter. The advent of advanced beam and large acceptance detector technologies has driven the development of highly polarized, full angular acceptance targets. The Crystal Ball detector with its unique capability to cope with multi photon final states is used in Mainz at the A2 real photon facility in combination with a frozen spin polarized target. Technical highlights from the development of thin superconducting magnets to provide a longitudinal and transverse polarization are presented. A continuous polarization in the ‘DNP’-mode is on the way. Another promising technology investigation is going in the direction of ‘Active Polarized Targets’ to use the target as an intrinsic part of the detector. This requires from the scintillating material and front-end electronics to operate at cryogenic temperatures.

scholarly journals Dark scalars and heavy neutral leptons at DarkQuest

2021 ◽  
Vol 2021 (5) ◽  
Author(s):  
Brian Batell ◽  
Jared A. Evans ◽  
Stefania Gori ◽  
Mudit Rai
Keyword(s):  
Particle Production ◽  
Meson Production ◽  
Gluon Fusion ◽  
New Physics ◽  
Dark Sector ◽  
Hidden Sector ◽  
Detector Acceptance ◽  
Light Scalar ◽  
Near Term

Abstract The proposed DarkQuest beam dump experiment, a modest upgrade to the existing SeaQuest/SpinQuest experiment, has great potential for uncovering new physics within a dark sector. We explore both the near-term and long-term prospects for observing two distinct, highly-motivated hidden sector benchmark models: heavy neutral leptons and Higgs-mixed scalars. We comprehensively examine the particle production and detector acceptance at DarkQuest, including an updated treatment of meson production, and light scalar production through both bremsstrahlung and gluon-gluon fusion. In both benchmark models, DarkQuest will provide an opportunity to probe previously inaccessible interesting regions of parameter space on a fairly short timescale when compared to other proposed experiments.

scholarly journals Studying neutron structure at Jefferson Lab through electron scattering off the deuteron, using CLAS12 and the Central Neutron Detector

2020 ◽  
Vol 1643 (1) ◽  
pp. 012191
Author(s):  
Paul Naidoo ◽  
Daria Sokhan ◽  
Pierre Chatagnon ◽  
Silvia Niccolai ◽  
Katheryne Price
Keyword(s):  
Neutron Detector ◽  
Meson Production ◽  
Deeply Virtual Compton Scattering ◽  
Virtual Compton Scattering ◽  
High Energy ◽  
Neutral Meson ◽  
Deuteron Target ◽  
Jefferson Lab ◽  
3D Tomography ◽  
Large Acceptance

Abstract Generalised Parton Distributions (GPDs) offer a way of imaging nucleons through 3D tomography. They can be accessed experimentally in processes such as Deeply Virtual Compton Scattering (DVCS) and Deeply Virtual Meson Production (DVMP), where a high energy electron scatters from a quark inside a nucleon and a high energy photon or meson is produced as a result. Jefferson Lab has recently completed its energy upgrade and Hall B houses the new, large-acceptance CLAS12 detector array optimised for measurements of DVCS and DVMP in the newly accessible kinematic regime. Measurements on the proton and neutron are complementary and both are necessary to facilitate access to the full set of GPDs and enable their flavour separation. Neutron DVCS and DVMP are possible with the use of a deuteron target – the first CLAS12 experiment with which has started taking data this year. To enable exclusive reconstruction of DVCS and neutral-meson DVMP, a dedicated detector for recoiling neutrons – the Central Neutron Detector (CND) – was integrated into CLAS12. We present the first CLAS12 deuteron-target experiment, with a focus on the performance of the CND.

scholarly journals Four-Quark States from Functional Methods

2020 ◽  
Vol 61 (4) ◽  
Author(s):  
Gernot Eichmann ◽  
Christian S. Fischer ◽  
Walter Heupel ◽  
Nico Santowsky ◽  
Paul C. Wallbott
Keyword(s):  
Symmetry Breaking ◽  
Scalar Meson ◽  
Chiral Symmetry Breaking ◽  
The Other ◽  
Feature Article ◽  
Exotic Mesons ◽  
Scalar Mesons ◽  
Functional Methods ◽  
Internal Structures ◽  
Light Scalar

AbstractIn this feature article we summarise and highlight aspects of the treatment of four-quark states with functional methods. Model approaches to those exotic mesons almost inevitably have to assume certain internal structures, e.g. by grouping quarks and antiquarks into (anti-)diquark clusters or heavy-light $$q{\bar{q}}$$ q q ¯ pairs. Functional methods using Dyson–Schwinger and Bethe–Salpeter equations can be formulated without such prejudice and therefore have the potential to put these assumptions to test and discriminate between such models. So far, functional methods have been used to study the light scalar-meson sector and the heavy-light sector with a pair of charmed and a pair of light quarks in different quantum number channels. For all these states, the dominant components in terms of internal two-body clustering have been identified. It turns out that chiral symmetry breaking plays an important role for the dominant clusters in the light meson sector (in particular for the scalar mesons) and that this property is carried over to the heavy-light sector. Diquark-antidiquark components, on the other hand, turn out to be almost negligible for most states with the exception of open-charm heavy-light exotics.

RECENT RESULTS FROM THE REAL PHOTON EXPERIMENT AT MAMI

2010 ◽  
Vol 19 (05n06) ◽  
pp. 1064-1075
Author(s):  
ANDREAS THOMAS
Keyword(s):  
High Intensity ◽  
Photon Beam ◽  
Real Photon ◽  
Final States ◽  
Detection Capability ◽  
Crystal Ball ◽  
The Real ◽  
The Future ◽  
Set Up

Experiments with real photons have been performed for many years at the Mainz accelerator MAMI with different detectors. The upgraded MAMI C accelerator recently delivered electrons with an energy of 1604MeV. The A2 collaboration performs experiments with energy tagged polarised real photons produced via 'Bremsstrahlung'. Linear and circular photon polarisation is possible. In the years 2005/2006 the Crystal Ball detector with its unique detection capability for multi photon final states was set up in Mainz. The Crystal Ball at MAMI setup offers an excellent possibility to study decays of the η and η′ mesons. Due to the high intensity photon beam the apparatus can be seen as an η-factory. Recent results from the Crystal Ball experiment at MAMI are presented. In the future we plan to use a longitudinal and transverse polarised frozen spin target to investigate the spin polarisibilities of the nucleons.

Sign in / Sign up

Export Citation Format

Share Document