We investigate the possibilities of using measurements in present and future experiments on heavy ion collisions to answer some longstanding problems in hadronic physics, namely identifying hadronic molecular states and exotic hadrons with multiquark components. The yields of a selected set of exotic hadron candidates in relativistic heavy ion collisions are discussed in the coalescence model in comparison with the statistical model. We find that the yield of a hadron is typically an order of magnitude smaller when it is a compact multiquark state, compared to that of an excited hadronic state with normal quark numbers. We also find that some loosely bound hadronic molecules are formed more abundantly than the statistical model prediction by a factor of two or more. Moreover, due to the significant numbers of charm and bottom quarks produced at RHIC and even larger numbers expected at LHC, some of the proposed heavy exotic hadrons could be produced with sufficient abundance for detection, making it possible to study these new exotic hadrons in heavy ion collisions.

We investigate quarkonium mass spectra in external constant magnetic fields by using QCD sum rules. We first discuss a general framework of QCD sum rules necessary for properly extracting meson spectra from current correlators computed in the presence of strong magnetic fields, that is, a consistent treatment of mixing effects caused in the mesonic degrees of freedom. We then implement operator product expansions for pseudoscalar and vector heavy-quark current correlators by taking into account external constant magnetic fields as operators, and obtain mass shifts of the lowestlying bound states ηc and J/ψ in the static limit with their vanishing spatial momenta. Comparing results from QCD sum rules with those from hadronic effective theories, we find that the dominant origin of mass shifts comes from a mixing between ηc and J/ψ with a longitudinal spin polarization, accompanied by other subdominant effects such as mixing with higher excited states and continua.

We investigate the properties of charmonia in strong magnetic fields by using QCD sum rules. We show how to implement the mixing effects between η(c) and J/ψ on the basis of field-theoretical approaches, and then show that the sum rules are saturated by the mixing effects with phenomenologically determined parameters. Consequently, we find that the mixing effects are the dominant contribution to the mass shifts of the static charmonia in strong magnetic fields.

We study the K * meson reduction in heavy ion collisions by focusing on the hadronic effects on the K * meson abundance. We evaluate the absorption cross sections of the K * and K meson by light mesons in the hadronic matter, and further investigate the variation in the meson abundances for both particles during the hadronic stage of heavy ion collisions. We show how the interplay between the interaction of the K * meson and kaon with light mesons in the hadronic medium determines the final yield difference of the statistical hadronization model to the experimental measurements. For the central Au+Au collision at √ sNN = 200 GeV, we find that the K * /K yield ratio at chemical freeze-out decreases by 36% during the expansion of the hadronic matter, resulting in the final ratio comparable to STAR measurements of 0.23 ±0.05.

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High energy heavy ion collisions are excellent ways for producing heavy hadrons and composite particles, including the light (anti)nuclei. With upgraded detectors at the Relativistic Heavy Ion Collider (RHIC) and the Large Hadron Collider (LHC), it has become possible to measure hadrons beyond their ground states. Therefore, heavy ion collisions provide a new method for studying exotic hadrons that are either molecular states made of various hadrons or compact system consisting of multiquarks. Because their structures are related to the fundamental properties of Quantum Chromodynamics (QCD), studying exotic hadrons is currently one of the most active areas of research in hadron physics. Experiments carried out at various accelerator facilities have indicated that some exotic hadrons may have already been produced. The present review is a summary of the current understanding of a selected set of exotic particle candidates that can be potentially measured in heavy ion collisions. It also includes discussions on the production of resonances, exotics and hadronic molecular states in these collisions based on the coalescence model and the statistical model. A more detailed discussion is given on the results from these models, leading to the conclusion that the yield of a hadron that is a compact multiquark state is typically an order of magnitude smaller than if it is an excited hadronic state with normal quark numbers or a loosely bound hadronic molecule. Attention is also given to some of the proposed heavy exotic hadrons that could be produced with sufficient abundance in heavy ion collisions because of the significant numbers of charm and bottom quarks that are produced at RHIC and even larger numbers at LHC, making it possible to study them in these experiments. Further included in the discussion are the general formalism for the coalescence model that involves resonance particles and its implication on the present estimated yield for resonance production. 1 arXiv:1702.00486v1 [nucl-th] 1 Feb 2017Finally, a review is given on recent studies to constrain the hadron-hadron interaction through correlation measurements in heavy ion collisions and their implications on the interpretation and the possible existence of exotic states in hadronic interactions.

We study the hadronic effects on the X(3872) meson abundance in heavy ion collisions. We evaluate the absorption cross sections of the X(3872) meson by pions and rho mesons in the hadronic stage of heavy ion collisions, and further investigate the variation in the X(3872) meson abundance during the expansion of the hadronic matter for its two possible quantum number states; J P = 1 + and 2 − . We show that the absorption cross sections and the time evolution of the X(3872) meson abundance are strongly dependent on the structure and quantum number of the X(3872) meson. We thus suggest that studying the abundance of the X(3872) meson in relativistic heavy ion collisions provides a chance to infer its quantum number as well as its structure.

The planetary gear hybrid powertrain (PGHP) is known as one of the most efficient configurations for hybrid electric vehicles. The system controls the speed and torque of each component so that it can produce adequate input and output speeds for the optimal operation of the total system. In this paper, the system mechanism is analysed to understand the relation between the input and output speeds. In addition, the transmission efficiency is expressed as a function of three parameters based on the calculation of the net output power. The characteristics of the transmission system showed a large difference from those of a conventional CVT. The speed ratio was the key parameter that affected the efficiency. Furthermore, the performances of the electric motor and generator were decisive factors owing to the loss in the energy conversion. In a simulation on an urban driving schedule, the optimal operation of the engine was able to be obtained, and the system showed an improvement of 2.2 per cent in fuel economy.