22 research outputs found
A tetraquark or not a tetraquark: A holography inspired stringy hadron (HISH) perspective
We suggest to use the state , which decays predominantly to
, as a window to the landscape of tetraquarks. We
propose a simple criterion to decide whether a state is a genuine stringy
exotic hadron - a tetraquark - or a "molecule". If it is the former it should
be on a (modified) Regge trajectory. We present the predictions of the mass and
width of the higher excited states on the trajectory. We argue that
there should exist an analogous "" state that decays to
and describe its trajectory. We conjecture also a
similar trajectory for tetraquarks containing strange quarks, and the modified
Regge trajectories can in fact be predicted for any resonances found decaying
to a baryon-antibaryon pair. En route to the results regarding tetraquarks, we
also make some additional predictions on higher excited charmonium states. We
briefly discuss the zoo of exotic stringy hadrons and in particular we sketch
all the possibilities of tetraquark states.Comment: v1: 28 pages, v2: typos fixed, references added, 29 pages, v3:
revised, published version, 30 page
Rotating strings confronting PDG mesons
We revisit the model of mesons as rotating strings with massive endpoints and
confront it with meson spectra. We look at Regge trajectories both in the
(J,M2) and (n,M2) planes, where J and n are the angular momentum and radial
excitation number respectively. We start from states comprised of u and d
quarks alone, move on to trajectories involving s and c quarks, and finally
analyze the trajectories of the heaviest observed b-bbar mesons. The endpoint
masses provide the needed transition between the linear Regge trajectories of
the light mesons to the deviations from linear behavior encountered for the
heavier mesons, all in the confines of the same simple model. From our fits we
extract the values of the quark endpoint masses, the Regge slope (string
tension) and quantum intercept. The model also allows for a universal fit where
with a single value of the Regge slope we fit all the (J,M2) trajectories
involving u, d, s, and c quarks. We include a list of predictions for higher
mesons in both J and n.Comment: v2: typos fixed and reference added, 47 pages / v3: added section in
appendix detailing the states used in the fits, 51 page
A rotating string model versus baryon spectra
We continue our program of describing hadrons as rotating strings with
massive endpoints. In this paper we propose models of baryons and confront them
with the baryon Regge trajectories. We show that these are best fitted by a
model of a single string with a quark at one endpoint and a diquark at the
other. This model is preferred over the Y-shaped string model with a quark at
each endpoint. We show how the model follows from a stringy model of the
holographic baryon which includes a baryonic vertex connected with N_c strings
to flavor probe branes. From fitting to baryonic data we find that there is no
clear evidence for a non-zero baryonic vertex mass, but if there is such a mass
it should be located at one of the string endpoints. The available baryon
trajectories in the angular momentum plane (J,M^2), involving light, strange,
and charmed baryons, are rather well fitted when adding masses to the string
endpoints, with a single universal slope of 0.95 GeV^-2. Most of the results
for the quark masses are then found to be consistent with the results extracted
from the meson spectra in a preceding paper, where the value of the slope
emerging from the meson fits was found to be 0.90 GeV^-2. In the plane of
quantum radial excitations, (n,M^2), we also find a good agreement between the
meson and baryon slopes. The flavor structure of the diquark is examined, where
our interest lies in particular on baryons composed of more than one quark
heavier than the u and d quarks. For these baryons we present a method of
checking the holographic interpretation of our results.Comment: v2: typos corrected, references added, 41 pages; v3: added some
sentences to clarify the relation between our model and the holograhic
string, 42 page
Glueballs as rotating folded closed strings
In previous papers we argued that mesons and baryons can be described as
rotating open strings in holographic backgrounds. Now we turn to closed
strings, which should be the duals of glueballs. We look at the rotating folded
closed string in both flat and curved backgrounds.
A basic prediction of the closed string model is that the slope of Regge
trajectories is half that of open strings. We propose that a simple method to
identify glueballs is to look for resonances that belong to trajectories with a
slope of approximately 0.45 GeV^-2, half the meson slope. We therefore look at
the experimental spectra of flavorless light mesons to see if such a scheme,
where some of the states are placed on open string trajectories and some on
closed ones, can fit known experimental data. We look at the f_0 (J^PC = 0^++)
and f_2 (2^++) resonances. As there is no preference for a single scheme of
sorting the different states into meson and glueball trajectories, we present
several possibilities, each identifying a different state as the glueball. We
supplement each scheme with predictions for the masses of excited glueballs.
We show that the width of the decay into two mesons is different for
glueballs and mesons thus providing a supplementary tool to distinguish between
them. In addition, we look at some lattice QCD results for glueball spectra and
check their compatibility with the closed string model.
One of the main conclusions of this paper is that an extension of
experimental data on the spectrum of flavorless hadrons is needed, in
particular in the region between around 2.4 GeV and 3 GeV.Comment: v1: 43 pages, v2: references added, 44 pages, v3: references added,
44 page
The decay width of stringy hadrons
In this paper we further develop a string model of hadrons by computing their
strong decay widths and comparing them to experiment. The main decay mechanism
is that of a string splitting into two strings. The corresponding total decay
width behaves as where and are the tension and
length of the string and is a dimensionless universal constant. We show
that this result holds for a bosonic string not only in the critical dimension.
The partial width of a given decay mode is given by
where is a phase
space factor, is the mass of the "quark" and "antiquark" created at
the splitting point, and is a dimensionless coefficient close to unity.
Based on the spectra of hadrons we observe that their (modified) Regge
trajectories are characterized by a negative intercept. This implies a
repulsive Casimir force that gives the string a "zero point length". We fit the
theoretical decay width to experimental data for mesons on the trajectories of
, , , , , , , and , and of the
baryons , , , and . We examine both the linearity
in and the exponential suppression factor. The linearity was found to agree
with the data well for mesons but less for baryons. The extracted coefficient
for mesons is indeed quite universal. The exponential
suppression was applied to both strong and radiative decays. We discuss the
relation with string fragmentation and jet formation. We extract the
quark-diquark structure of baryons from their decays. A stringy mechanism for
Zweig suppressed decays of quarkonia is proposed and is shown to reproduce the
decay width of states. The dependence of the width on spin and
flavor symmetry is discussed. We further apply this model to the decays of
glueballs and exotic hadrons.Comment: v1: 98 pages / v2: minor revisions, references added, 100 pages (41
figures) / v3: final published version, minor corrections, 100 page
Excited mesons, baryons, glueballs and tetraquarks: Predictions of the Holography Inspired Stringy Hadron model
In this note we collect and summarize the predictions of the Holography
Inspired Stringy Hadron (HISH) model. We list the masses and widths of
predicted excited states across the spectrum, based on placing the different
hadrons on the non-linear Regge trajectories of a string with massive
endpoints. Our predicted states include: (i) Light, heavy-light and heavy-heavy
mesons. (ii) Baryons, including charmed, doubly charmed and bottom baryons.
(iii) Glueballs, together with a method to disentangle them from flavorless
mesons. (iv) Genuine tetraquarks, which are not "molecules" of hadrons, and are
characterized by their decay into a baryon and an anti-baryon.Comment: v1: 45 pages. v2: typos corrected, references added, 45 page
Deciphering the recently discovered tetraquark candidates around 6.9 GeV
Recently a novel hadronic state of mass 6.9 GeV, that decays mainly to a pair
of charmonia, was observed in LHCb. The data also reveals a broader structure
centered around 6490 MeV and suggests another unconfirmed resonance centered at
around 7240 MeV, very near to the threshold of two doubly charmed
baryons. We argue in this note that these exotic hadrons are genuine
tetraquarks and not molecules of charmonia. It is conjectured that they are
V-baryonium tetraquarks, namely, have an inner structure of a baryonic vertex
with a diquark attached to it, which is connected by a string to an
anti-baryonic vertex with a anti-diquark. We examine these
states as the analogs of the states and /
which are charmonium-like tetraquarks. One way to test these claims is by
searching for a significant decay of the state at 7.2 GeV into
. Such a decay would be the analog of the decay of
the state into to . We further argue
that there should be trajectories of both orbital and radial excited states of
the . We predict their masses. It is possible that a few of these
states have already been seen by LHCb.Comment: v1: 22 pages, 4 figures v2: typos corrected, minor additions and
references added. 22 pages, v3: references added. 22 page
A measure for chaotic scattering amplitudes
We propose a novel measure of chaotic scattering amplitudes. It takes the
form of a log-normal distribution function for the ratios
of (consecutive) spacings between
two (consecutive) maxima of the scattering amplitude. We show that the same
measure applies to the quantum mechanical scattering on a leaky torus as well
as to the decay of highly excited string states into two tachyons. Quite
remarkably the obey the same distribution that governs the non-trivial
zeros of Riemann zeta function.Comment: v2: small corrections, references adde