Time-like Proton Form Factors with Initial State Radiation Technique

Electromagnetic form factors are fundamental quantities describing the internal structure of hadrons. They can be measured with scattering processes in the space-like region and annihilation processes in the time-like region. The two regions are connected by crossing symmetry. The measurements of the proton electromagnetic form factors in the time-like region using the initial state radiation technique are reviewed. Recent experimental studies have shown that initial state radiation processes at high luminosity electron-positron colliders can be effectively used to probe the electromagnetic structure of hadrons. The BABAR experiment at the B-factory PEP-II in Stanford and the BESIII experiment at BEPCII (an electron positron collider in the τ-charm mass region) in Beijing have measured the time-like form factors of the proton using the initial state radiation process e+e−→pp¯γ. The two kinematical regions where the photon is emitted from the initial state at small and large polar angles have been investigated. In the first case, the photon is in the region not covered by the detector acceptance and is not detected. The Born cross section and the proton effective form factor have been measured over a wide and continuous range of the the momentum transfer squared q2 from the threshold up to 42 (GeV/c)2. The ratio of electric and magnetic form factors of the proton has been also determined. In this report, the theoretical aspect and the experimental studies of the initial state radiation process e+e−→pp¯γ are described. The measurements of the Born cross section and the proton form factors obtained in these analyses near the threshold region and in the relatively large q2 region are examined. The experimental results are compared to the predictions from theory and models. Their impact on our understanding of the nucleon structure is discussed

Measurement of proton electromagnetic form factors using the initial-state-radiation process e+e- ppgamma at BESIII

The electromagnetic structure of the proton can be studied by measuring the electromagnetic form factors. In the time-like kinematic region, several experiments have been performed in the last two decades. However, limited statistics in most cases only allowed for extraction of the effective form factor of the proton. Only few experiments have been able to extract the ratio of the electric and magnetic form factors of the proton, with uncertainties larger than 11%. The results of the ratio from different experiments show strong discrepancies in the momentum-transferred region close to the proton-antiproton pair ($pbar{b}$) production threshold. In this thesis, the proton electromagnetic form factors are studied via the initial-state-radiation process $e^{+}e^{-}to pbar{p}gamma$. The total luminosity used amounts to 7.41 fb$^{-1}$, collected at seven center-of-mass energies between 3.773 and 4.600 GeV with the BESIII spectrometer at the BEPCII collider. Two scenarios can be distinguished depending on whether the radiated photon is detected (tagged case, around 12% of the events) or not (untagged case, around 40% of the events). In the analysis with the radiated photon tagged, the ratio of proton form factors is extracted for six bins of the momentum transfer from 1.877 to 3.0 GeV/c. The statistical and systematic uncertainties range from 18.5% to 33.6% and 4.5% to 15.6%, respectively. The cross section of $e^{+}e^{-}to pbar{p}$ and the effective form factor of the proton are measured in bins of 25 MeV/c width from 1.877 to 2.3 GeV/c, and in bins of 50 MeV/c width from 2.3 to 3.0 GeV/c, with statistical uncertainties at the 10% level. In the analysis with the radiated photon untagged, the cross section and the effective form factor are measured from 2.0 to 3.8 GeV/c with uncertainties at the few-percent level. The ratio is extracted for four bins from 2.0 to 3.0 GeV/c, with statistical and systematic uncertainties from 24.8% to 35.4% and 7.1% to 14.8%, respectively. The measurements presented in this work are essential for further understanding of the $e^{+}e^{-}to pbar{p}$ process and the proton electromagnetic form factors in a wide momentum-transferred region. Close to the $pbar{p}$ threshold, the ratio of proton form factors confirms the results from BABAR and CMD-3, conflicting with PS170. At higher momentum transfers, the ratio of proton form factors is consistent with existing measurements. The cross section and the effective form factor are in a good agreement with previous measurements at the few-percent precision level

Time-like Proton Form Factors with Initial State Radiation Technique

Electromagnetic form factors are fundamental quantities describing the internal structure of hadrons. They can be measured with scattering processes in the space-like region and annihilation processes in the time-like region. The two regions are connected by crossing symmetry. The measurements of the proton electromagnetic form factors in the time-like region using the initial state radiation technique are reviewed. Recent experimental studies have shown that initial state radiation processes at high luminosity electron-positron colliders can be effectively used to probe the electromagnetic structure of hadrons. The BABAR experiment at the B-factory PEP-II in Stanford and the BESIII experiment at BEPCII (an electron positron collider in the τ-charm mass region) in Beijing have measured the time-like form factors of the proton using the initial state radiation process e+e−→pp¯γ. The two kinematical regions where the photon is emitted from the initial state at small and large polar angles have been investigated. In the first case, the photon is in the region not covered by the detector acceptance and is not detected. The Born cross section and the proton effective form factor have been measured over a wide and continuous range of the the momentum transfer squared q2 from the threshold up to 42 (GeV/c)2. The ratio of electric and magnetic form factors of the proton has been also determined. In this report, the theoretical aspect and the experimental studies of the initial state radiation process e+e−→pp¯γ are described. The measurements of the Born cross section and the proton form factors obtained in these analyses near the threshold region and in the relatively large q2 region are examined. The experimental results are compared to the predictions from theory and models. Their impact on our understanding of the nucleon structure is discussed

Optimal OFDM channel estimation with carrier frequency offset and phase noise

Abstract-We propose an optimal training-based OFDM channel impulse response (CIR) estimation algorithm that addresses the phase noise (PHN) and carrier frequency offset (CFO) problem. If left unattended, these combined problems severely degrade the accuracy of the channel estimate and ultimately the quality of the wireless link. The solution involves the joint optimization of a complete log-likelihood function over the unknown CIR, PHN and CFO. To reduce the complexity of the proposed algorithm, a simplification based on the conjugate gradient method is introduced, yielding an efficient realization using the Fast Fourier Transform (FFT) with only minor performance degradation

Current Status and Future Prospects for the Light Dark Matter eXperiment

The constituents of dark matter are still unknown, and the viable possibilities span a vast range of masses. The physics community has established searching for sub-GeV dark matter as a high priority and identified accelerator-based experiments as an essential facet of this search strategy. A key goal of the accelerator-based dark matter program is testing the broad idea of thermally produced sub-GeV dark matter through experiments designed to directly produce dark matter particles. The most sensitive way to search for the production of light dark matter is to use a primary electron beam to produce it in fixed-target collisions. The Light Dark Matter eXperiment (LDMX) is an electron-beam fixed-target missing-momentum experiment that realizes this approach and provides unique sensitivity to light dark matter in the sub-GeV range. This contribution provides an overview of the theoretical motivation, the main experimental challenges, how LDMX addresses these challenges, and projected sensitivities. We further describe the capabilities of LDMX to explore other interesting new and standard physics, such as visibly-decaying axion and vector mediators or rare meson decays, and to provide timely electronuclear scattering measurements that will inform the modeling of neutrino-nucleus scattering for DUNE.Comment: 26 pages, 17 figures. Contribution to Snowmass 202