From Tetraquark to Hexaquark: A Systematic Study of Heavy Exotics in the Large NcN_c Limit

A systematic study of multiquark exotics with one or $N_c-1$ heavy quarks in the large $N_c$ limit is presented. By binding a chiral soliton to a heavy meson, either a normal $N_c$-quark baryon or an exotic $(N_c+2)$-quark baryon is obtained. By replacing the heavy quark with $N_c-1$ heavy antiquarks, exotic $(2N_c-2)$-quark and $2N_c$-quark mesons are obtained. When $N_c = 3$, they are just the normal triquark baryon $Qqq$, the exotic pentaquark baryon $Q\bar q\bar q\bar q\bar q$, tetraquark di-meson $\bar Q \bar Q qq$ and the hexaquark di-baryon $\bar Q \bar Q \bar q \bar q\ bar q \bar q$ respectively. Their stabilities and decays are also discussed. In particular, it is shown that the ``heavy to heavy'' semileptonic decays are described by the Isgur--Wise form factors of the normal baryons.Comment: 14 pages in REVTeX, no Figure

Nuclear dependence coefficient α(A,qT)\alpha(A,q_T) for the Drell-Yan and J/ψ\psi production

Define the nuclear dependence coefficient $\alpha(A,q_T)$ in terms of ratio of transverse momentum spectrum in hadron-nucleus and in hadron-nucleon collisions: $\frac{d\sigma^{hA}}{dq_T^2}/ \frac{d\sigma^{hN}}{dq_T^2}\equiv A^{\alpha(A,q_T)}$. We argue that in small $q_T$ region, the $\alpha(A,q_T)$ for the Drell-Yan and J/$\psi$ production is given by a universal function:\ $a+b q_T^2$, where parameters a and b are completely determined by either calculable quantities or independently measurable physical observables. We demonstrate that this universal function $\alpha(A,q_T)$ is insensitive to the A for normal nuclear targets. For a color deconfined nuclear medium, the $\alpha(A,q_T)$ becomes strongly dependent on the A. We also show that our $\alpha(A,q_T)$ for the Drell-Yan process is naturally linked to perturbatively calculated $\alpha(A,q_T)$ at large $q_T$ without any free parameters, and the $\alpha(A,q_T)$ is consistent with E772 data for all $q_T$.Comment: latex, 28 pages, 10 figures, updated two figures, and add more discussion

D* Production in Deep Inelastic Scattering at HERA

This paper presents measurements of D^{*\pm} production in deep inelastic scattering from collisions between 27.5 GeV positrons and 820 GeV protons. The data have been taken with the ZEUS detector at HERA. The decay channel $D^{*+}\to (D^0 \to K^- \pi^+) \pi^+$ (+ c.c.) has been used in the study. The $e^+p$ cross section for inclusive D^{*\pm} production with $5<Q^2<100 GeV^2$ and $y<0.7$ is 5.3 \pms 1.0 \pms 0.8 nb in the kinematic region {$1.3<p_T(D^{*\pm})<9.0$ GeV and $| \eta(D^{*\pm}) |<1.5$}. Differential cross sections as functions of p_T(D^{*\pm}), $\eta(D^{*\pm}), W$ and $Q^2$ are compared with next-to-leading order QCD calculations based on the photon-gluon fusion production mechanism. After an extrapolation of the cross section to the full kinematic region in p_T(D^{*\pm}) and $\eta$(D^{*\pm}), the charm contribution $F_2^{c\bar{c}}(x,Q^2)$ to the proton structure function is determined for Bjorken $x$ between 2 $\cdot$ 10$^{-4}$ and 5 $\cdot$ 10$^{-3}$.Comment: 17 pages including 4 figure

Observation of Scaling Violations in Scaled Momentum Distributions at HERA

Charged particle production has been measured in deep inelastic scattering (DIS) events over a large range of $x$ and $Q^2$ using the ZEUS detector. The evolution of the scaled momentum, $x_p$, with $Q^2,$ in the range 10 to 1280 $GeV^2$, has been investigated in the current fragmentation region of the Breit frame. The results show clear evidence, in a single experiment, for scaling violations in scaled momenta as a function of $Q^2$.Comment: 21 pages including 4 figures, to be published in Physics Letters B. Two references adde

High-p_T pion and kaon production in relativistic nuclear collisions

High-p_T pion and kaon production is studied in relativistic proton-proton, proton-nucleus, and nucleus-nucleus collisions in a wide energy range. Cross sections are calculated based on perturbative QCD, augmented by a phenomenological transverse momentum distribution of partons (``intrinsic k_T''). An energy dependent width of the transverse momentum distribution is extracted from pion and charged hadron production data in proton-proton/proton-antiproton collisions. Effects of multiscattering and shadowing in the strongly interacting medium are taken into account. Enhancement of the transverse momentum width is introduced and parameterized to explain the Cronin effect. In collisions between heavy nuclei, the model over-predicts central pion production cross sections (more significantly at higher energies), hinting at the presence of jet quenching. Predictions are made for proton-nucleus and nucleus-nucleus collisions at RHIC energies.Comment: 26 pages in Latex, 19 EPS figure

Forward jet production in deep inelastic ep scattering and low-x parton dynamics at HERA

Differential inclusive jet cross sections in neutral current deep inelastic ep scattering have been measured with the ZEUS detector. Three phase-space regions have been selected in order to study parton dynamics where the effects of BFKL evolution might be present. The measurements have been compared to the predictions of leading-logarithm parton shower Monte Carlo models and fixed-order perturbative QCD calculations. In the forward region, QCD calculations at order alpha_s^1 underestimate the data up to an order of magnitude at low x. An improved description of the data in this region is obtained by including QCD corrections at order alpha_s^2, which account for the lowest-order t-channel gluon-exchange diagrams, highlighting the importance of such terms in parton dynamics at low x.Comment: 25 pages, 4 figure

Cronin effect and energy conservation constraints in high energy proton-nucleus collisions

We estimate the Cronin effect in pA collisions at the CERN LHC and at RHIC, using a Glauber-Eikonal model of initial state multiparton interactions. For a correct determination of the initial parton flux, we upgrade the model cross section, taking carefully into account all kinematical constraints of each multi-parton interaction process. As compared with previous results, derived with approximate kinematics, we obtain a softer spectrum of produced partons, while improving the agreement of the model with the recent measurements of neutral pions production in d+Au collisions at sqrt(s)=200 AGeV.Comment: Accepted by Phys.Rev.

Measurement of the reaction γ∗p→ϕp\gamma^*p \rightarrow \phi p in deep inelastic e+pe^+p scattering at HERA

The production of phi mesons in the reaction e(+)p --> e(+)phi p (phi --> K+K-), for 7 phi p cross section rises strongly with W. This behaviour is similar to that previously found for the gamma*p --> rho(0)p cross section. This strong dependence cannot be explained by production through soft pomeron exchange, It is, however, consistent with perturbative QCD expectations, where it reflects the rise of the gluon momentum density in the proton at small x. The ratio of sigma(phi)/sigma(rho(0)), which has previously been determined by ZEUS to be 0.065 +/- 0.013 (stat.) in photoproduction at a mean W of 70 GeV, is measured to be 0.18 +/- 0.05 (stat.) +/- 0.03 (syst.) at a mean Q(2) of 12.3 GeV2 and mean W of approximate to 100 GeV and is thus approaching at large Q(2) the value of 2/9 predicted from the quark charges of the vector mesons and a flavour independent production mechanism

Observation of Events with an Energetic Forward Neutron in Deep Inelastic Scattering at HERA

In deep inelastic neutral current scattering of positrons and protons at the center of mass energy of 300 GeV, we observe, with the ZEUS detector, events with a high energy neutron produced at very small scattering angles with respect to the proton direction. The events constitute a fixed fraction of the deep inelastic, neutral current event sample independent of Bjorken x and Q2 in the range 3 · 10-4 \u3c xBJ \u3c 6 · 10-3 and 10 \u3c Q2 \u3c 100 GeV2

Age at first birth in women is genetically associated with increased risk of schizophrenia

Prof. Paunio on PGC:n jäsenPrevious studies have shown an increased risk for mental health problems in children born to both younger and older parents compared to children of average-aged parents. We previously used a novel design to reveal a latent mechanism of genetic association between schizophrenia and age at first birth in women (AFB). Here, we use independent data from the UK Biobank (N = 38,892) to replicate the finding of an association between predicted genetic risk of schizophrenia and AFB in women, and to estimate the genetic correlation between schizophrenia and AFB in women stratified into younger and older groups. We find evidence for an association between predicted genetic risk of schizophrenia and AFB in women (P-value = 1.12E-05), and we show genetic heterogeneity between younger and older AFB groups (P-value = 3.45E-03). The genetic correlation between schizophrenia and AFB in the younger AFB group is -0.16 (SE = 0.04) while that between schizophrenia and AFB in the older AFB group is 0.14 (SE = 0.08). Our results suggest that early, and perhaps also late, age at first birth in women is associated with increased genetic risk for schizophrenia in the UK Biobank sample. These findings contribute new insights into factors contributing to the complex bio-social risk architecture underpinning the association between parental age and offspring mental health.Peer reviewe