Haiyan Gao

Haiyan Gao
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Haiyan Gao

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Nuclear Experiment (10)
High Energy Physics - Experiment (9)
High Energy Physics - Phenomenology (6)
Nuclear Theory (5)
Physics - Atomic Physics (1)
High Energy Physics - Lattice (1)
Physics - Instrumentation and Detectors (1)

Publications Authored By Haiyan Gao

The electric dipole moment (EDM), which violates both parity and time-reversal symmetries, is one of the most sensitive probes of new physics beyond the standard model. Nucleons as the main building blocks of the visible universe provide a natural laboratory for the exploration of additional CP violation sources to understand the baryogenesis mechanism. The nucleon tensor charge, which can be measured through semi-inclusive deep inelastic scattering (SIDIS) processes, is a fundamental QCD quantity that measures the transversely polarized quark number in a transversely polarized proton. Read More

We investigate the hidden strange light baryon-meson system. With the resonating-group method, two bound states, $\eta-N$ and $\phi-N$, are found in the quark delocalization color screening model. Focusing on the $\phi-N$ bound state around 1950 MeV, we obtain the total decay width of about 4 MeV by calculating the phase shifts in the resonance scattering processes. Read More

We propose a novel method to search for possible new macro-scale spin- and/or velocity-dependent forces (SVDFs) based on specially designed SmCo$_5$ spin sources and a spin exchange relaxation-free (SERF) comagnetometer. A simulation shows that, by covering a SmCo$_5$ permanent magnet with a layer of pure iron, a high net spin density source of about $1\times 10^{22}$/cm$^3$ could be obtained. Taking advantages of the high spin density of this iron-shielded SmCo$_5$ and the high sensitivity of the SERF, the proposed method could set up new limits of greater than 10 orders of magnitude more sensitive than those from previous experiments or proposals in exploring SVDFs in force ranges larger than 1 cm. Read More

Future experiments at the Jefferson Lab 12 GeV upgrade, in particular, the Solenoidal Large Intensity Device (SoLID), aim at a very precise data set in the region where the partonic structure of the nucleon is dominated by the valence quarks. One of the main goals is to constrain the quark transversity distributions. We apply recent theoretical advances of the global QCD extraction of the transversity distributions to study the impact of future experimental data from the SoLID experiments. Read More

This document presents the recommendations and scientific conclusions from the Town Meeting on QCD and Hadronic Physics that took place in the period 13-15 September 2014 at Temple University as part of the NSAC 2014 Long Range Planning process. It highlights progress in hadron physics in the seven years since the 2007 Long Range Plan (LRP07), and presents a vision for the future by identifying key questions and plausible paths to solutions which should define our next decade. In defining the priority of outstanding physics opportunities for the future, both prospects for the short (roughly 5 years) and longer term (beyond 10 years) are identified together with the facilities, personnel and other resources needed to maximize the discovery potential in hadronic physics worldwide. Read More

The possible existence of short-range forces between unpolarized and polarized spin-1/2 particles has attracted the attention of physicists for decades. These forces are predicted in various theories and provide a possible new source for parity (P) and time reversal (T) symmetry violation. We use an ensemble of polarized 3He gas in a cell with a 250 um thickness glass window to search for a force from scalar boson exchange over a sub-millimeter ranges. Read More

Recent evidence for the existence of pentaquark $\Theta^+$ particle from several experiments at several different laboratories around the world has caused great excitement and raised many unanswered questions. We discuss a new proposal on a high resolution experiment searching for pentaquark states in Hall C at Jefferson Lab using an untagged bremsstrahlung photon beam employing both the hydrogen and the deuterium targets by studying the following processes: $\gamma p \to \Theta^{++} K^-$, and $\gamma n \to \Theta^+ K^-$. This new experiment will significantly improve our current knowledge of the mass, the width of the $\Theta^+$ particle if it is confirmed and provide unambiguous evidence for the existence or non-existence of the $\Theta^{++}$ particle from the \gamma p \to \Theta^{++} K^-$ process. Read More

The $\gamma n \to \pi^- p$ and $\gamma p \to \pi^+ n$ reactions are essential probes of the transition from meson-nucleon degrees of freedom to quark-gluon degrees of freedom in exclusive processes. The cross sections of these processes are also advantageous, for the investigation of oscillatory behavior around the quark counting prediction, since they decrease relatively slower with energy compared with other photon-induced processes. In this talk, we discuss recent results on the $\gamma p \to \pi^+ n$ and $\gamma n \to \pi^{-}p$ processes from Jefferson Lab experiment E94-104. Read More

The nucleon electromagnetic form factors have been studied in the past extensively from unpolarized electron scattering experiments. With the development in polarized beam, recoil polarimetry, and polarized target technologies, polarization experiments have provided more precise data on these quantities. In this talk, I review recent experimental progress on this subject. Read More

It is shown that the exotic non-qqq hadrons of pentaquark $qqqq\bar{q}$ states can be clearly distinguished from the conventional qqq-baryon resonances or their hybrids if the flavor of $\bar{q}$ is different from any of the other four quarks. We suggest the physical process $p(e,e'K^-)Z(uuud\bar{s})$, which can be investigated at the Thomas Jefferson National Accelerator Facility (JLab), as an ideal process to search for the existence or non-existence of the exotic hadron of minimal pentaquark state $Z(uuud\bar{s})$. (The search for the existence of $Z(uudd\bar{s})$ is also discussed in the paper. Read More

Nucleon electromagnetic form factors are fundamental quantities related to the charge and magnetization distributions inside the nucleon. Understanding the nucleon electromagnetic structure in terms of the underlying quark and gluon degrees of freedom of quantum chromodynamics is a challenging and urgent task. The nucleon electromagnetic form factors have been studied in the past extensively from unpolarized electron scattering experiments. Read More