463 research outputs found
Charmed Baryonium
We re-analyze the published data on the Y(4630) --> Lambda_c Lambdabar_c and
the Y(4660) --> psi(2S) pi pi with a consistent Ansatz and we find that the two
observations are likely to be due to the same state Y_B with M_{Y_B} = 4660.7
+- 8.7 MeV and Gamma_{Y_B} = 61 +- 23 MeV. Under this hypothesis and
reanalizing also the e+e- --> J/psi pi pi gamma_ISR spectrum we extract B(Y_B
--> Lambda_c Lambdabar_c) / B(Y_B --> psi(2S) pi pi) = 25 +- 7, B(Y_B --> J/psi
pi pi) / B(Y_B --> psi(2S) pi pi) J/psi pi pi)
/ B(Y(4350) --> psi(2S) pi pi) psi(2S)
sigma) / B (Y_B --> psi(2S) f_0)=2.0 +- 0.3. These conclusions strongly support
the hypothesis of Y_B being the first observation of a charmed baryonium
constituted by four quarks. From the analysis of the mass spectrum and the
decay properties we show that Y(4350) and Y_B are respectively consistent with
the ground state and first radial excitation of the L=1 state.Comment: Corrected phase space normalization in the fit
The 2^-+ assignment for the X(3872)
Very recently the BaBar collaboration has put forward a claim that the
X(3872) is not a 1^++ resonance, as most of the phenomenological work on the
subject was relying on, but rather a 2^-+ one. We examine the consequences of
this quantum number assignment for the solution of the X(3872) puzzle. The
molecular interpretation appears less likely, and the conventional charmonium
interpretation should be reconsidered. There are several well-known
difficulties with this interpretation, to which we add a new one: the
production cross section at CDF is predicted to be much smaller than that
observed. We also confirm, using a relativistic string model, the conclusion
from potential models that the mass of the state is not consistent with
expectations. In the tetraquark interpretation the 2^-+ assignment implies a
rich spectrum of partner states, although the X(3872) may be among the few
which are narrow enough to be observable.Comment: 18 pages, 6 figures, 4 tables; minor style corrections. Version to
appear in PR
Update on Counting Valence Quarks at RHIC
We update our former analysis of the Nuclear Modification Factors (NMF) for
different hadron species at RHIC and LHC. This update is motivated by the new
experimental data from STAR which presents differences with the preliminary
data used to fix some of the parameters in our model. The main change is the
use of AKK fragmentation functions for the hard part of the spectrum and minor
adjustments of the coalescence (soft) contribution. We confirm that observation
of the NMF for the f_0 meson can shed light on its quark composition.Comment: 4 pages, 4 figure
J/psi dissociation by light mesons in an extended Nambu Jona-Lasinio model
An alternative model for the dissociation of the J/psi is proposed. Chiral
symmetry is properly implemented. Abnormal parity interactions and mesonic form
factors naturally arise from the underlying quark sub-structure. Analytic
confinement for the light quarks is generated by appropriately chosen the quark
interaction kernels. Dissociation cross sections of the J/psi by either a pion
or a rho meson are then evaluated and discussed.Comment: 24 pages, 13 figures, final versio
The momentum distribution of J/psi in B decays
The discrepancy between theory and data in the momentum distribution of slow
J/psi in B decays has been several times addressed as a puzzle. Using the most
recent results on exclusive B decays into J/psi and heavy kaons or exotic
mesons and reconsidering the non-relativistic-QCD calculation of the color
octet fragmentation component, we show that an improvement in the comparison
between data and theory can be obtained. There is still room for a better fit
to data and this may imply that new exotic mesons of the XYZ kind have yet to
be discovered.Comment: 4 pages, 2 figures, 2 tables. To appear in Physical Review
Carbon nanotubes as target for directional detection of light WIMP
In this paper I will briefly introduce the idea of using Carbon Nanotubes
(CNT) as target for the detection of low mass WIMPs with the additional
information of directionality. I will also present the experimental efforts of
developing a Time Projection Chamber with a CNT target inside and the results
of a test beam at the Beam Test Facility of INFN-LNF.Comment: 3 figures, IFAE2017 poster session proceeding
J/psi couplings to charmed resonances and to pi
We present an evaluation of the strong couplings JD^(*)D^(*) and
JD^(*)D^(*)pi by an effective field theory of quarks and mesons. These
couplings are necessary to calculate pi+J/psi --> D^(*)+barD^(*) cross
sections, an important background to the J/psi suppression signal in the
quark-gluon plasma. We write down the general effective lagrangian and compute
the relevant couplings in the soft pion limit and beyond.Comment: 11 pages, 4 figures, 2 reference added and minor comments, style
changed to RevTe
More loosely bound hadron molecules at CDF?
In a recent paper we have proposed a method to estimate the prompt production
cross section of X(3872) at the Tevatron assuming that this particle is a
loosely bound molecule of a D and a D*bar meson. Under this hypothesis we find
that it is impossible to explain the high prompt production cross section found
by CDF at sigma(X(3872)) \sim 30-70 nb as our theoretical prediction is about
300 times smaller than the measured one. Following our work, Artoisenet and
Braaten, have suggested that final state interactions in the DD*bar system
might be so strong to push the result we obtained for the cross section up to
the experimental value. Relying on their conclusions we show that the
production of another very narrow loosely bound molecule, the X_s=D_s D_s*bar,
could be similarly enhanced. X_s should then be detectable at CDF with a mass
of 4080 MeV and a prompt production cross section of sigma(X_s) \sim 1-3 nb.Comment: Minor revisions made. To appear in Phys Lett
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