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Single particle strength restoration and nuclear transparency in high Q^2 exclusive (e,e'p) reactions  [PDF]
L. Frankfurt,M. Strikman,M. Zhalov
Physics , 2000, DOI: 10.1016/S0370-2693(01)00173-3
Abstract: Quenching of the single particle strength which previously precluded unambiguous measurement of nuclear transparency in quasifree (e,e'p) reactions at high momentum transfer is evaluated from the cross sections of measured processes. We have demonstrated evidence of the single particle strength restoration with increase of the momentum transfer in exclusive (e,e'p) reactions and argue that in practically interesting cases of study the nuclear transparency in these processes quenching is weakly depends on the probability of short range nucleon correlations. It is shown that use of Glauber approximation well describes NE18 and E94-139 (e,e'p) data at the momentum transfers 1 GeV^2 < Q^2 < 3 GeV^2. This gives a further support to our observation that the quenching of nuclear levels strongly depends on the resolution (Q^2)and practically disappears at Q^2>1GeV^2.
Hadron Helicity Violation in Exclusive Processes: Quantitative Calculations in Leading Order QCD  [PDF]
T. Gousset,B. Pire,J. P. Ralston
Physics , 1995, DOI: 10.1103/PhysRevD.53.1202
Abstract: We study a new mechanism for hadronic helicity flip in high energy hard exclusive reactions. The mechanism proceeds in the limit of perfect chiral symmetry, namely without any need to flip a quark helicity. The fundamental feature of the new mechanism is the breaking of rotational symmetry of the hard collision by a scattering plane in processes involving independent quark scattering. We show that in the impulse approximation there is no evidence for of the helicity violating process as the energy or momentum transfer $Q^2$ is increased over the region 1 GeV^2 < Q^2 < 100 GeV^2. In the asymptotic region Q^2> 1000 GeV^2, a saddle point approximation with doubly logarithmic accuracy yields suppression by a fraction of power of Q^2. ``Chirally--odd" exclusive wave functions which carry non--zero orbital angular momentum and yet are leading order in the high energy limit, play an important role.
Excited Baryon Structure Using Exclusive Reactions with CLAS12  [PDF]
Daniel S. Carman
Physics , 2015,
Abstract: Studying excited nucleon structure through exclusive electroproduction reactions is an important avenue for exploring the nature of the non-perturbative strong interaction. Electrocouplings for $N^*$ states in the mass range below 1.8~GeV have been determined from analyses of CLAS $\pi N$, $\eta N$, and $\pi \pi N$ data. This work made it clear that consistency of independent analyses of exclusive channels with different couplings and non-resonant backgrounds but the same $N^*$ electro-excitation amplitudes, is essential to have confidence in the extracted results. In terms of hadronic coupling, many high-lying $N^*$ states preferentially decay through the $\pi \pi N$ channel instead of $\pi N$. Data from the $KY$ channels will therefore be critical to provide an independent analysis to compare the extracted electrocouplings for the high-lying $N^*$ states against those determined from the $\pi N$ and $\pi \pi N$ channels. A program to study excited $N^*$ decays to non-strange and strange exclusive final states using CLAS12 will measure differential cross sections to be used as input to extract the $\gamma_vNN^*$ transition form factors for the most prominent $N^*$ states in the range of invariant energy $W$ up 3~GeV in the virtually unexplored domain of momentum transfers $Q^2$ up to 12~GeV$^2$.
Inclusive and Exclusive Scatterings from Tensor Polarized Deuteron  [PDF]
Misak M. Sargsian,Mark I. Strikman
Physics , 2014, DOI: 10.1088/1742-6596/543/1/012009
Abstract: The possibility of using a tensor polarized deuteron target in electroproduction reactions creates new opportunities for studying different phenomena related to the short-range hadronic and nuclear physics. The use of tensor polarized deuteron allows to isolate smaller than average inter-nucleon distances for the bound two-nucleon system. In this report we consider several of high $Q^2$ reactions which are particularly sensitive to the short-range two-nucleon configurations in the deuteron. The one is the relativistic dynamics of electron-bound-nucleon scattering which can be studied in both inclusive and exclusive reactions, other is the strong final state interaction in close proximity of two nucleons that can be used as a sensitive probe for color-transparency phenomena.
Exclusive Photon-Induced Hadronic Reactions at Large Momentum Transfers  [PDF]
W. Schweiger
Physics , 1995,
Abstract: It is generally assumed that due to factorization of long- and short-distance dynamics perturbative QCD can be applied to exclusive hadronic reactions at large momentum transfers. Within such a perturbative approach diquarks turn out to be a useful phenomenological device to model non-perturbative effects still observable in the kinematic range accessible by present-days experiments. The basic ingredients of the perturbative formalism with diquarks, i.e. Feynman rules for diquarks and quark-diquark wave functions of baryons, are briefly summarized. Applications of the diquark model to the electromagnetic form factors of the proton in the space- as well as time-like region, Compton-scattering off protons, gamma-gamma -> p-pbar, and photoproduction of Kaons are discussed.
Strangeness Suppression in q-qbar Creation Observed in Exclusive Reactions  [PDF]
K. Park,M. D. Mestayer,the CLAS collaboration
Physics , 2014, DOI: 10.1103/PhysRevLett.113.152004
Abstract: We measured the ratios of electroproduction cross-sections from a proton target for three exclusive meson-baryon final states: $\Lambda K^+$, $p\pi^0$, and $n\pi^+$, with the CLAS detector at Jefferson Lab. Using a simple model of quark hadronization we extract q-qbar creation probabilities for the first time in exclusive two-body production, in which only a single q-qbar pair is created. We observe a sizable suppression of strange quark-antiquark pairs compared to non-strange pairs, similar to that seen in high-energy production.
Test of QCD at large $Q^2$ with exclusive hadronic processes  [PDF]
Chengping Shen for the Belle Collaboration
Physics , 2014,
Abstract: My report consists of two parts: (1). Using samples of 102 million $\Upsilon(1S)$ and 158 million $\Upsilon(2S)$ events at Belle, we study 17 exclusive hadronic decays of these two bottomonium resonances to some Vector-Pseudoscalar (VP), Vector-Tensor (VT) and Axial-vector-Pseudoscalar (AP) processes and their final states. Branching fractions are measured for all the processes. The ratios of the branching fractions of $\Upsilon(2S)$ and $\Upsilon(1S)$ decays into the same final state are used to test a perturbative QCD (pQCD) prediction for OZI-suppressed bottomonium decays. (2). Using data samples of 89 fb$^{-1}$, 703 fb$^{-1}$, and 121 fb$^{-1}$ collected at center-of-mass (CMS) energies 10.52, 10.58, and 10.876~GeV, respectively, we measure the cross sections of $e^+e^- \to \omega\pi^0$, $K^{\ast}(892)\bar{K}$, and $K_2^{\ast}(1430)\bar{K}$. The energy dependence of the cross sections is presented.
Studies of exotic hadrons by high-energy exclusive reactions  [PDF]
H. Kawamura,S. Kumano,T. Sekihara
Physics , 2013,
Abstract: We investigate the possibility of clarifying internal structure of exotic hadrons by high-energy exclusive reactions. In particular, the constituent-counting rule could be used for determining the internal configuration in large-angle exclusive scattering. As an example, we show the cross section pi^- + p -> K^0 + Lambda(1405) in comparison with the one for the ground-state Lambda production pi^- + p -> K^0 + Lambda. The counting rule indicates that the cross section scales as s^8 dsigma /dt=constant if Lambda(1405) is an ordinary three-quark baryon, whereas it is s^{10} dsigma /dt=constant if Lambda(1405) is a five-quark baryon. Here, s and t are Mandelstam variables. Such experiments could be possible at J-PARC, LEP, JLab, CERN-COMPASS, and other high-energy facilities.
Internal structure of exotic hadrons by high-energy exclusive reactions  [PDF]
H. Kawamura,S. Kumano,T. Sekihara
Physics , 2014,
Abstract: We propose to use high-energy exclusive reactions for probing internal structure of exotic hadron candidates. First, the constituent counting rule of perturbative QCD can be used for finding internal configurations of an exotic hadron candidate. It is because the number of constituents ($n$), which participate in the exclusive reaction, is found by the scaling behavior of the cross section $d\sigma/dt \propto 1/s^{n-2}$ at large momentum transfer, where $s$ is the center-of-mass energy squared. As an example, we show that the internal structure of $\Lambda \, (1405)$ should be found, for example, by the reaction $\pi^- + p \to K^0 + \Lambda (1405)$. Second, the internal structure of exotic hadron candidates should be investigated by hadron tomography with generalized parton distributions (GPDs) and generalized distribution amplitudes (GDAs) in exclusive reactions. Exotic nature should be reflected in the GPDs which contain two factors, longitudinal parton distributions as indicated by the constituent counting rule and transverse form factors as suggested by the hadron size. The GDAs should be investigated by the two-photon process $\gamma^* \gamma \to h\bar h$, for example $h=f_0$ or $a_0$, in electron-positron annihilation. Since the GDAs contain information on a time-like form factor, exotic nature should be found by studying the $h\bar h$ invariant mass dependence of the cross section. The internal structure of exotic hadron candidates should be clarified by the exclusive reactions at facilities such as J-PARC and KEKB.
Free Quarks and Antiquarks versus Hadronic Matter
Xu, Xiao-Ming;Peng, Ru
High Energy Physics - Phenomenology , 2007,
Abstract: Meson-meson reactions A(q_1 \bar{q}_1) + B(q_2 \bar{q}_2) to q_1 + \bar{q}_1 + q_2 + \bar{q}_2 in high-temperature hadronic matter are found to produce an appreciable amount of quarks and antiquarks freely moving in hadronic matter and to establish a new mechanism for deconfinement of quarks and antiquarks in hadronic matter.
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