arXiv subjects

Marek Karliner

Publications and source records attributed to Marek Karliner.

At least 37 records · Page 2Linked to original sources

arXiv2018

Strange baryons with two heavy quarks

The LHCb Experiment at CERN has observed a doubly-charmed baryon $Ξ_{cc}^{++} =ccu$ with a mass of $3621.40 \pm 0.78$ MeV, consistent with many predictions. We use the same methods that led us to predict $M(Ξ_{cc},~J^P{=}1/2^+) = 3627 \pm 12$ MeV and $M(Ξ_{cc}^*,~J^P{=}3/2^+) = 3690 \pm 12$ MeV to predict $M(Ω_{cc}^+,J^P{=}1/2^+) = 3692 \pm 16$ MeV and $M(Ω_{cc}^*,~J^P{=} 3/2^+) = 3756 \pm 16$ MeV. Production and decay are discussed briefly, and predictions for $M(Ω_{bc})$ and $M(Ω_{bb})$ are included.

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arXiv2017

Multiquark States

Why do we see certain types of strongly interacting elementary particles and not others? This question was posed over 50 years ago in the context of the quark model. M. Gell-Mann and G. Zweig proposed that the known mesons were $q \bar q$ and baryons $qqq$, with quarks known at the time $u$ ("up"), $d$ ("down"), and $s$ ("strange") having charges (2/3,-1/3,-1/3). Mesons and baryons would then have integral charges. Mesons such as $qq \bar q \bar q$ and baryons such as $qqqq \bar q$ would also have integral charges. Why weren't they seen? They have now been seen, but only with additional heavy quarks and under conditions which tell us a lot about the strong interactions and how they manifest themselves. The present article describes recent progress in our understanding of such "exotic" mesons and baryons.

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arXiv2017

Quark-level analogue of nuclear fusion with doubly-heavy baryons

The recent discovery by LHCb of the first doubly-charmed baryon $Ξ_{cc}^{++} = ccu$ at $3621.40 \pm 0.78$ MeV implies a large binding energy $\sim 130$ MeV between the two $c$ quarks. This strong binding enables a quark-rearrangement exothermic reaction $\,Λ_c Λ_c \to Ξ_{cc}^{++}\,n\,$ with $Q=12$ MeV, which is a quark-level analogue of deuterium-tritium nuclear fusion reaction $DT\to {}^4{\rm He}\,n$. Due to much larger binding energy between two $b$ quarks $\sim 280$ MeV, the analogous reaction with $b$ quarks, $\,Λ_b Λ_b \to Ξ_{bb}\,N\,$ is expected to have a dramatically larger $Q$-value, $138\pm 12$ MeV.

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arXiv2017

Discovery of doubly-charmed Xi_{cc} baryon implies a stable (b b ubar dbar) tetraquark

Recently LHCb discovered the first doubly-charmed baryon $Ξ_{cc}^{++} = ccu$ at $3621.40 \pm 0.78$ MeV, very close to our theoretical prediction. We use the same methods to predict a doubly-bottom tetraquark $T(bb\bar u\bar d)$ with $J^P{=}1^+$ at $10,389\pm 12$ MeV, 215 MeV below the $B^-\bar B^{*0}$ threshold and 170 MeV below threshold for decay to $B^-\bar B^0 γ$. The $T(bb\bar u\bar d)$ is therefore stable under strong and electromagnetic (EM) interactions and can only decay weakly, the first exotic hadron with such a property. On the other hand, the mass of $T(cc\bar u\bar d)$ with $J^P{=}1^+$ is predicted to be $3882\pm12$ MeV, 7 MeV above the $D^0 D^{*+}$ threshold and 148 MeV above $D^0 D^+ γ$ threshold. $T(bc\bar u\bar d)$ with $J^P{=}0^+$ is predicted at $7134\pm13$ MeV, 11 MeV below the $\bar B^0 D^0$ threshold. Our precision is not sufficient to determine whether $bc\bar u\bar d\,$ is actually above or below the threshold. It could manifest itself as a narrow resonance just at threshold.

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arXiv2017

Isospin splittings in baryons with two heavy quarks

Isospin splittings in baryons with two heavy quarks and a $u$ or $d$ quark are calculated using simple methods proposed previously by the authors. The results are $M(Ξ_{cc}^{++})-M(Ξ_{cc}^+) = 1.41 \pm 0.12^{+0.76}$ MeV, $M(Ξ_{bb}^0) - M(Ξ_{bb}^-) = - 4.78 \pm 0.06^{+0.03}$ MeV, and $M(Ξ_{bc}^+)-M(Ξ_{bc}^0)=-1.69 \pm0.07 ^{+0.39}$ MeV, where the statistical errors reflect uncertainties in input mass splittings, and the systematic errors are associated with the choice of constituent-quark masses.

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arXiv2017

$J/ψN$ photoproduction on deuterium as a test for exotic baryons

We extend a previous study of photoproduction of exotic baryon resonances to the reaction $γ+ d \to J/ψ+ n + p$, which permits simultaneous investigation of the reactions $γ+ p \to P_c^+ \to J/ψ~p$ \hbox{($n$ spectator)} and $γ+ n \to P_c^0 \to J/ψ~n$ \hbox{($p$ spectator).} Here $P_c^+$ is an exotic baryon with quark content $c \bar c uud$, and $P_c^0$ is its hypothetical isospin partner with quark content $c \bar c ddu$. We find: \hbox{(1) The} cross section for $J/ψ~n$ photoproduction should be equal to that for $J/ψ~p$ photoproduction if these processes are dominated by the photon coupling to a $c\bar c$ pair. In that case the two processes are equal by isospin reflection. (2) If a $P_c^+$ candidate is a genuine $c \bar c u u d$ resonance, its isospin partner $P_c^0 = c \bar c d d u$ should have the same mass (again by isospin reflection). (3) In the absence of Fermi motion, the cross section for photoproduction of $P_c$ off a deuteron should be nearly the sum of two equal cross sections: $σ(γp \to P_c^+)$ (spectator $n$) and $σ(γn \to P_c^0)$ (spectator $p$). (4) The effects of Fermi motion are significant. They include smearing, form-factor suppression and offshellness. The upshot is that the resonance is significantly wider and the peak cross section off a deuteron is expected to be considerably less than twice that in $γp$.

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arXiv2017

Very narrow excited $Ω_c$ baryons

Recently LHCb reported the discovery of five extremely narrow excited $Ω_c$ baryons decaying into $Ξ_c^+ K^-$. We interpret these baryons as bound states of a $c$-quark and a $P$-wave $ss$-diquark. For such a system there are exactly five possible combinations of spin and orbital angular momentum. The narrowness of the states could be a signal that it is hard to pull apart the two $s$-quarks in a diquark. We predict two of spin 1/2, two of spin 3/2, and one of spin 5/2, all with negative parity. Of the five states two can decay in $S$-wave and three can decay in $D$-wave. Some of the $D$-wave states might be narrower than the $S$-wave states. We discuss relations among the five masses expected in the quark model and the likely spin assignments and compare with the data. A similar pattern is expected for negative-parity excited $Ω_b$ states. An alternative interpretation is noted in which the heaviest two states are $2S$ excitations with $J^P = 1/2^+$ and $3/2^+$, while the lightest three are those with $J^P = 3/2^-,3/2^-,5/2^-$ expected to decay via $D$-waves. In this case we expect $J^P = 1/2^-$ $Ω_c$ states around 2904 and 2978 MeV.

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arXiv2017

$Q Q \bar Q \bar Q$ states: masses, production, and decays

The question of whether there exist bound states of two heavy quarks $Q=(c,b)$ and antiquarks $\bar Q = (\bar c, \bar b)$, distinct from a pair of quark-antiquark mesons, has been debated for more than forty years. We suggest some means of producing and observing $Q_1 Q_2 \bar Q_3 \bar Q_4$ resonant states, concentrating on the $c c \bar c \bar c$ channel which is most easily produced and the $b b \bar b \bar b$ channel which has a better chance of being relatively narrow. We obtain $M_{(cc)(\bar c \bar c)} = 6,192 \pm 25$ MeV and $M_{(bb)(\bar b \bar b)} = 18,826 \pm 25$ MeV, for the charmed and bottom tetraquarks, respectively. Experimental search for these states in the relevant mass region is highly desirable.

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arXiv2016

Exotic resonances due to $η$ exchange

The meson $X(3872)$ and several related states appear to be, at least in part, hadronic molecules in which a heavy flavored meson (such as $D^0$) is bound to another heavy meson (such as $\bar D^{*0}$). Although not the only effect contributing to the binding, pion exchange seems to play a crucial role in generating the longest-range force between constituents. Mesons without $u$ and $d$ light quarks (such as $D_s$) cannot exchange pions, but under suitable circumstances can bind as a result of $η$ exchange. Channels in which this mechanism is possible are identified, and suggestions are made for searches for the corresponding molecular states, including a manifestly exotic baryonic $Λ_c \bar D_s^*$ resonance decaying into $J/ψ~Λ$.

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arXiv2015

Photoproduction of Exotic Baryon Resonances

We point out that the new exotic resonances recently reported by LHCb in the $J/ψp$ channel are excellent candidates for photoproduction off a proton target. This test is crucial to confirming the resonant nature of such states, as opposed to their being kinematical effects. We specialize to an interpretation of the heavier narrow state as a molecule composed of $Σ_c$ and $\bar D^*$, and estimate its production cross section using vector dominance. The relevant photon energies and fluxes are well within the capabilities of the GlueX and CLAS12 detectors at Thomas Jefferson National Accelerator Facility (JLAB). A corresponding calculation is also performed for photoproduction of an analogous resonance which is predicted to exist in the $Υp$ channel.

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arXiv2015

Prospects for observing the lowest-lying odd-parity $Σ_c$ and $Σ_b$ baryons

There exist candidates for the negative-parity states $Λ_{c,b}(1/2^-, 3/2^-)$ consisting of an isospin-zero, spin-zero light diquark $[ud]$ with one unit of orbital angular momentum with respect to a $c,b$ quark. However, there exists only one candidate for the orbital excitations of the $Σ_c(1/2^+)$ and $Σ_c^*(3/2^+)$, and none for the orbital excitations of $Σ_b(1/2^+)$ or $Σ_b^*(3/2^+)$. We extend a previous discussion of odd-parity $Λ_{c,b}$ states and explore some patterns of the odd-parity $Σ_{c,b}$ baryons consisting of a light isospin-one nonstrange diquark $(uu,ud,dd)$ in a state of $L=1$ with respect to the spin-1/2 heavy quark $(c,b)$.

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arXiv2015

New Exotic Meson and Baryon Resonances from Doubly-Heavy Hadronic Molecules

We predict several new exotic doubly-heavy hadronic resonances, inferring from the observed exotic bottomonium-like and charmonium-like narrow states $X(3872)$, $Z_b(10610)$, $Z_b(10650)$, $Z_c(3900)$, and $Z_c(4020/4025)$. We interpret the binding mechanism as mostly molecular-like isospin-exchange attraction between two heavy-light mesons in a relative S-wave state. We then generalize it to other systems containing two heavy hadrons which can couple through isospin exchange. The new predicted states include resonances in meson-meson, meson-baryon, baryon-baryon, and baryon-antibaryon channels. These include those giving rise to final states involving a heavy quark $Q=c,b$ and antiquark $\bar Q' = \bar c,\bar b$, namely $D \bar D^*$, $D^* \bar D^*$, $D^* B^*$, $\bar B B^*$, $\bar B^* B^*$, $Σ_c \bar D^*$, $Σ_c B^*$, $Σ_b \bar D^*$, $Σ_b B^*$, $Σ_c \bar Σ_c$, $Σ_c \bar Λ_c$, $Σ_c \bar Λ_b$, $Σ_b \bar Σ_b$, $Σ_b \bar Λ_b$, and $Σ_b \bar Λ_c$, as well as corresponding S-wave states giving rise to $Q Q'$ or $\bar Q \bar Q'$.

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arXiv2015

Radiative Return Capabilities of a High-Energy, High-Luminosity $e^+e^-$ Collider

An electron-positron collider operating at a center-of-mass energy $E_{CM}$ can collect events at all lower energies through initial-state radiation (ISR or radiative return). We explore the capabilities for radiative return studies by a proposed high-luminosity collider at $E_{CM}$ = 250 or 90 GeV, to fill in gaps left by lower-energy colliders such as PEP, PETRA, TRISTAN, and LEP. These capabilities are compared with those of the lower-energy $e^+e^-$ colliders as well as hadron colliders such as the Tevatron and the CERN Large Hadron Collider (LHC). Some examples of accessible questions in dark photon searches and heavy flavor spectroscopy are given.

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arXiv2014

$X(3872)$, $X_b$, and the $χ_{b1}(3P)$ state

We discuss the possible production and discovery channels in $e^+e^-$ and $pp$ machines of the $X_b$, the bottomonium counterpart of $X(3872)$ and the putative isoscalar analogue of the charged bottomonium-like states $Z_b$ discovered by Belle. We suggest that the $X_b$ may be close in mass to the bottomonium state $χ_{b1}(3P)$, mixing with it and sharing its decay channels, just as $X(3872)$ is likely a mixture of a $\bar D D^*$ molecule and $χ_{c1}(2P)$. Consequently, the experiments which reported observing $χ_{b1}(3P)$ might have actually discovered the $X_b$, or a mixture of the two states.

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arXiv2014

Baryons with two heavy quarks: Masses, production, decays, and detection

The large number of $B_c$ mesons observed by LHCb suggests a sizable cross section for producing doubly-heavy baryons in the same experiment. Motivated by this, we estimate masses of the doubly-heavy $J=1/2$ baryons $Ξ_{cc}$, $Ξ_{bb}$, and $Ξ_{bc}$, and their $J=3/2$ hyperfine partners, using a method which accurately predicts the masses of ground-state baryons with a single heavy quark. We obtain $M(Ξ_{cc}) = 3627 \pm 12$ MeV, $M(Ξ_{cc}^*)= 3690 \pm 12$ MeV, $M(Ξ_{bb}) = 10162 \pm 12$ MeV, $M(Ξ_{bb}^*)= 10184 \pm 12$ MeV, $M(Ξ_{bc}) = 6914 \pm 13$ MeV, $M(Ξ'_{bc}) = 6933 \pm 12$ MeV, and $M(Ξ_{bc}^*) = 6969 \pm 14$ MeV. As a byproduct, we estimate the hyperfine splitting between $B_c^*$ and $B_c$ mesons to be $68 \pm 8$ MeV. We discuss P-wave excitations, production mechanisms, decay modes, lifetimes, and prospects for detection of the doubly heavy baryons.

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arXiv2014

Doubly Heavy Tetraquarks and Baryons

During the last three years strong experimental evidence from $B$ and charm factories has been accumulating for the existence of exotic hadronic quarkonia, narrow resonances which cannot be made from a quark and an antiquark. Their masses and decay modes show that they contain a heavy quark-antiquark pair, but their quantum numbers are such that they must also contain a light quark-antiquark pair. The theoretical challenge has been to determine the nature of these resonances. The main possibilities are that they are either "genuine tetraquarks", i.e. two quarks and two antiquarks within one confinement volume, or "hadronic molecules" of two heavy-light mesons. In the last few months there as been more and more evidence in favor of the latter. I discuss the experimental data and its interpretation and provide fairly precise predictions for masses and quantum numbers of the additional exotic states which are naturally expected in the molecular picture but have yet to be observed. In addition, I provide arguments in favor of the existence of an even more exotic state - a hypothetical deuteron-like bound state of two heavy baryons. I also consider "baryon-like" states $Q Q' \bar q\bar q'$, which if found will be direct evidence not just for near-threshold binding of two heavy mesons, but for genuine tetraquarks with novel color networks. I stress the importance of experimental search for doubly-heavy baryons in this context.

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arXiv2013

The doubly heavies: (Qbar Q qbar q), (Q Q qbar qbar) tetraquarks and (Q Q q) baryons

Recent discoveries by Belle and BESIII of charged exotic quarkonium-like resonances provide fresh impetus for study of heavy exotic hadrons. In the limit N_c --> infinity, M_Q --> infinity, the (Qbar Q qbar q') tetraquarks (TQ-s) are expected to be narrow and slightly below or above the (Qbar q') and (Q qbar) two-meson threshold. The isoscalar TQ-s manifest themselves by decay to (Qbar Q) pi pi, and the ~30 MeV heavier charged isotriplet TQ-s by decays into (Qbar Q) pi. The new data strongly suggest that the real world with N_c=3, Q=c,b and q,q' = u,d is qualitatively described by the above limit. We discuss the relevant theoretical estimates and suggest new signatures for TQ-s in light of the recent discoveries. We also consider "baryon-like" states (Q Q' qbar qbar'), which if found will be direct evidence not just for near-threshold binding of two heavy mesons, but for genuine tetraquarks with novel color networks. We stress the importance of experimental search for doubly-heavy baryons in this context.

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arXiv2013

Tetraquarks, their Masses and Decays in QED_2

Recent observations by Belle and BESIII of charged quarkonium-like resonances give new stimulus for theoretical investigation of exotic hadrons in general and heavy tetraquarks in particular. We use QED_2, a confining theory, as a model for the masses and decays of tetraquarks. Here we discuss the states (Q Qbar q qbar) and (Q Q qbar qbar) (and its anti-particle), where Q and q are two fermion flavors with masses M and m, so that M > m. We then discuss decay modes of these states into (Q Qqbar), (q qbar), (Q qbar), (Qbar q). It turns out that (Q Qbar q qbar) is stable, while (Q Q qbar qbar) is not.

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