Related papers: Pentaquark $\Theta^+$ search at HERMES

Recent spectroscopy studies performed in high energy ep collisions by the H1 and ZEUS Collaborations are described. The status of the searches for the strange pentaquark, the Theta+, is presented as well as results on searches for further…

Studying scattering of heavy flavor hadrons and looking for bound states is shown to give experimental information otherwise unobtainable about effective two-body interactions between constituent $(qq)_6$ and $(\bar qq)_8$ pairs…

Prompted by the recent surprising results in QCD spectroscopy, we extend to heavy flavors the hadron mass relations showing that the constituent quark mass differences and ratios have the same values when obtained from mesons and baryons.…

We discuss the properties of the pentaquark in a collective stringlike model with a nonplanar configuration of the four quarks and the antiquark. In an application to the mass spectrum of exotic Theta baryons, we find that the ground state…

We study here the $\Lambda_b^0 \to J/\psi p \pi^-$ reaction in analogy to the $\Lambda^0_b \to J/\psi p K^-$ one, and we note that in both decays there is a sharp structure (dip or peak) in the $J/\psi p$ mass distribution around $4450$…

This paper is a continuation of our studies of multiquark hadrons. The anti-symmetrization of their wavefunctions required by Fermi statistics is nontivial, as it mixes orbital, color, spin and flavor structures. In our previous papers we…

The e^+ jet invariant mass spectrum produced in the reaction e^+ p -> e^+ X has been studied at a center-of-mass energy of 300 GeV. The data were collected using the ZEUS detector operating at the HERA collider, and correspond to an…

Multiquark searches have been a hot topic in recent years. Some threshold enhancements were observed during the analysis of 58M $\jpsi$ events collected by BES II detector. These enhancements can't be explained by the standard model and may…

The classical quenched quark models with three constituent quarks provide a good description for the baryon spatial ground states, but fail to reproduce the spectrum of baryon excited states. More and more evidences suggest that unquenched…

A high-statistics experiment on a deuterium target was performed using a real photon beam with energies up to 3.6 GeV at the CLAS detector of Jefferson Lab. The reaction reported here is for $\gamma d \to p K^- K^+ n$ where the neutron was…

We consider the interplay of the pentaquark states and strange tetraquark states in the decay $\Lambda^0_b\to K^-J/\psi p$. Possible existence of ($cs\bar c\bar u$)-states is taken up and their manifestation in the $K^-J/\psi $-channel is…

There may exist seven $\bar D^{(*)} \Sigma_c^{(*)}$ hadronic molecular states. We construct their corresponding interpolating currents, and calculate their masses and decay constants using QCD sum rules. Based on these results, we calculate…

The exciting discovery by LHCb of the $P_c(4312)^+$ and $P_c(4450)^+$ pentaquarks, or the suggestion of a tetraquark nature for the $Z_c(3900)$ state seen at BESIII and Belle, have triggered a lot of activity in the field of hadron physics,…

The latest results from the H1 and ZEUS collaborations are presented on leptoquark production and rare Standard Model processes. The data were taken in the period 1994-2005, at a centre of mass energy of up to 319 GeV. Intriguing events…

The $J/\psi p$ signals at 4380 MeV and 4450 MeV which were seen by the LHCb collaboration in the decay $\Lambda^0_b\to K^-J/\psi p$ are discussed following the hypothesis of the existence of diquark-diquark-antiquark composite states. The…

The experimental evidence for pentaquarks, both old an new, is discussed. Constraints due to $K^+N$ scattering data from previous decades is first reviewed, followed by experiments with positive evidence and those with null results.…

We study the hadronic molecular structure of hidden heavy pentaquarks - new exotic states composed of charmed/bottom baryons and $D(D^*)/B(B^*)$ mesons. Based on the observation of three pentaquark candidates $P_c^+(4312)$, $P_c^+(4440)$,…

Experimental data from the 2m propane bubble chamber have been analyzed for exotic baryon states search. A number of peculiarities were found in the effective mass spectra of: $\Lambda \pi^+$($\Sigma^{*+}$(1382),PDG), $\Lambda p$ and…

Quark portal interactions $qqqN$ with a light singlet fermion $N$ make baryon number testable through missing transverse energy (MET). We find that present LHC data constrain scales up to 10 TeV (MET plus jet), 8 TeV (MET plus top) and 11…

We present the study of $\bar{B}^{0} \to \Sigma_{c}(2455)^{0,++} \pi^{\pm} \bar{p}$ decays based on $772\times 10^{6}$ $B\bar{B}$ events collected with the Belle detector at the KEKB asymmetric-energy $e^+e^-$ collider. The…