arXiv subjects
Publications and source records attributed to Harry J. Lipkin.
Basic 1966 physics of Sakharov, Zeldovich and Nambu updated by QCD with constituent-quark quasiparticles having effective masses fits all masses and magnetic moments of ground state meson and baryons having no more than one strange or heavy quark Flavor antisymmetry explains absence of low-lying exotics and suggests diquark-triquark model and two-state model for $Θ^+$ pentaquark. Variational approach gives mass bounds for other pentaquarks.
Is there a theory or good experimental evidence? Bj's question: Pentaquark is created by $e^+e^-$. $2q + q \to$ Baryon $; ~ ~ ~ 2q + \bar q \to $ Triquark$ ; ~ ~ ~ 2q + $Triquark $ \to $Pentaquark Does it live long onough to be observable? Basic physics of constituent quarks and flavor antisymmetry. Report of $Θ^+$ violating flavor antisymmetry indicates need for two-cluster model.. Ball in Experimental Court - Some experiments see $Θ^+$; others don't. Possible production mechanisms present in some experiments, absent in others; e.g. via $N^*(2.3 \rm{GeV}) \to Θ^+ + \bar K$?
The contradiction between evidence for and against the existence of the Theta+ pentaquark might be resolved if it only appears as a result of a particular production mechanism which is present in some experiments and absent in others. We examine the implications of Theta+ production via decay of a cryptoexotic N* resonance with a mass of about 2.4 GeV corresponding to a peak in the experimental data for the invariant mass of the (Theta+,K-) system. Further experimental checks are suggested.
This note has no new results and is therefore not intended to be submitted to a "research" journal in the foreseeable future, but to be available to the numerous individuals who are interested in this issue. The Debye-Waller factor is the ratio of the coherent scattering or absorption cross section of a photon or electron by particles bound in a complex system to the value for the same process on an analgous free particle. It is often interpreted also as the probability of the coherent process, normalized to unity, with the difference between unity and the Debye Waller factor interpreted as the probability of incoherent processes. The Debye-Waller factor is then interpreted as a measure of decoherence. The breakdown of this description for a test particle which cannot give or lose energy is not generally appreciated. Prime examples are: Bragg scattering, the Mössbauer effect and related phenomena at zero temperature. The physics of the change in the interpretation of the Debye-Waller factor is summarized here in a hopefully pedagogical manner.
We propose a model for the recently discovered Theta^+ exotic KN resonance as a novel kind of a pentaquark with an unusual color structure: a color triplet (ud) diquark, coupled to a color anti-triplet (ud s-bar) triquark in a relative P-wave. The state has J^P=1/2^+, I=0 and is an antidecuplet of SU(3)_f. A rough mass estimate of this pentaquark is close to experiment.
The narrow width of the exotic narrow baryon resonance $Θ^+$ might be explained by mixing between the two nearly degenerate states that arise in models with two diquarks and an antiquark. The only open $Θ^+$ decay channel is $KN$. When two states both coupled to a single dominant decay mode are mixed by the loop diagram via this decay mode, diagonalization of the loop diagram decouples one mass eigenstate from this decay mode as in some treatments of the $ρ-π$ decay from the mixed singlet-octet $ω-ϕ$ system, the $K^* -π$ decay of the strange axial vector mesons and the $NK$ couplings of some baryons. This mechanism can explain the narrow width and weak coupling of $Θ^+ \to KN$ while allowing a relatively large production cross section from $K^*$ exchange. Interesting tests are suggested in $K^-p$ reactions where backward kaon production must go by exotic baryon exchange.
The apparent symmetry between energy and momentum found in all covariant descriptions of neutrino oscillations is destroyed in the neutrino detector, a quantum mechanical system described by a density matrix diagonal in energy but not in momentum. The off diagonal matrix elements between states of different momenta and the same energy produce the coherence and interference between mass eigenstates having the same energy and different momenta that produce oscillations.
We consider nonleptonic Cabibbo--allowed $Λ_b$ decays in the factorization approximation. We calculate nonleptonic decays of the type $ Λ_b \to Λ_c P $ and $ Λ_b \to Λ_c V $ relative to $\bar{B}_d \to D^+ P$ and $\bar{B}_d \to D^+ V$ where we include among the pseudoscalar states(P) and the vector states(V) the newly discovered $D_s$ resonances, $D_s(2317)$ and $D_s(2460)$. In the ratio of $Λ_b$ decays to $D_s(2317)$ and $D_s(2460)$ relative to the $\bar{B}_d$ decays to these states, the poorly known decay constants of $D_s(2317)$ and $D_s(2460)$ cancel leading to predictions that can shed light on the nature of these new states. In general, we predict the $Λ_b$ decays to be larger than the corresponding $\bar{B}_d$ decays and in particular we find the branching ratio for $Λ_b \to Λ_c D_s(2460)$ can be between four to five times the branching ratio for $\bar{B}_d \to D^+ D_s(2460)$. This enhancement of $Λ_b$ branching ratios follows primarily from the fact that more partial waves contribute in $Λ_b$ decays than in $\bar{B}_d$ decays. Our predictions are largely independent of model calculations of hadronic inputs like form factors and decay constants.
Simple rigorous quantum mechanics with no hand waving nor loopholes clarifies the confusion between three contradictory descriptions of neutrino oscillations: (1)The time oscillations shown in standard textbooks produced by neutrino eigenstates with different masses and different energies. (2) That time oscillations and interference between states having different energies cannot be observed in realistic experiments. (3) That interference between different neutrino mass eigenstates is not observable in "missing mass" experiments where information determining the neutrino mass is available from other particles measured in production or detection vertices. Quantum-mechanical ignorance of the neutrino momentum is rigorously shown to be imposed by all realistic detectors and to produce coherence between amplitudes from neutrino states with the same energy and different masses. Conditions are precisely formulated for the loss of coherence when mass eigenstate wave packets moving with different velocities separate. The example of Bragg scattering shows how quantum-mechanically imposed ignorance produces coherence.
Motivated by the recent discovery of the exotic S=+1 narrow baryon resonance Theta^+ at 1540 MeV, with quark content {uudd sbar}, we conjecture the existence of its anti-charmed analogue Theta_c, with quark content {uudd cbar}, and compute its likely properties. We rely on the recently constructed model of a novel kind of a pentaquark with an unusual color structure which provides a good approximation to the Theta^+ mass. We expect that Theta_c is an isosinglet with J^P=1/2^+ and estimate its mass at 2985 \pm 50 MeV. We also discuss another possible exotic baryon resonance containing heavy quarks, the Theta_b^+, a {uudd bbar} state, and estimate m_{Theta_b^+}=6398 \pm 50 MeV. These states should appear as unexpectedly narrow peaks in D^-p, Dbar^0 n, B^0 p and B^+ n mass distributions.
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 obtain several new successful relations involving heavy quarks and provide some related predictions. We discuss in detail the apparent sharp decrease in m_s and m_c, when a light partner quark in a meson is replaced by a heavy one and construct a potential model which qualitatively reproduces this pattern through wave function effects. We apply these ideas to the recently discovered theta^+ exotic KN resonance and propose its interpretation as a novel kind of a pentaquark with an unusual color structure, J^P=1/2^+, I=0 and an antidecuplet of SU(3)_f. A rough mass estimate of this pentaquark is close to experiment.
The recent reported charmed-strange resonance at 2.32 GeV/c suggests a possible multiquark state. Three types of multiquark bound states are reviewed. A previous model-independent variational approach considers a tetraquark with two heavy antiquarks and two light quarks as a heavy antidiquark with the color field of a quark bound to the two light quarks with a wave function like that of a heavy baryon. Results indicate that a charmed-strange tetraquark $\bar c \bar s u d$ or a bottom-strange tetraquark $\bar b \bar s u d$ with this "diquark-heavy-baryion" wave function is not bound, in contrast to "molecular-type" $D-K$ and $B-K$ wave functions. However, a charmed-bottom tetraquark $\bar c \bar b u d$ might be bound with a very narrow weak decay mode. A "molecular-type" $D-B$ state can have an interesting $B_c π$ decay with a high energy pion,
Neutrino oscillations are experimentally observable only as a result of interference between neutrino states with different masses and THE SAME ENERGY. All interference effects between neutrino states having different energies are destroyed by the intereaction between the incident neutrino and the neutrino detector. Erroneous results are frequently obtained by neglecting the neutrino-detector interactions.
The past leaves the surprising experimental successes of the simple constituent quark model to be expained by QCD. Surprising agreement with experiment from simple Sakharov-Zeldovich model (1966) having quarks with effective masses and hyperfine interaction. Nambu's (1966) Colored quarks with gauge gluons gave mass spectrum with only $qqq$ and $\bar q$ bound states. The future opens the way to new insight into QCD from heavy flavor experiments
Radial mixing in the pseudoscalar $η-η^{\prime}$ systems can be generated from hyperfine interactions and annihilation terms. For the $η-η^{\prime}$ system we find the effects of radial mixing are appreciable and seriously affect the decay branching ratios for $B \to η(η^{\prime})K(K^*)$, mainly by modifying the $B \to η(η^{\prime})$ form factors. In particular, the effect of radial mixing in conjunction with the interference effects among penguin amplitudes can resolve puzzles in the $B \to η(η^{\prime}) K$ decays. The decay $Λ_b \to Λη(η^{\prime})$ on the other hand is dominated by a single amplitude so that the significant interference effects of B decays are absent here. Moreover, since no $Λ_b \to η(η^{\prime})$ form factors are involved here, the effect of radial mixing is essentially negligible. Hence, unlike the B system, we do not predict a large enhancement of $Λ_b \to Λη^{\prime}$ relative to $Λ_b \to Λη$.
We consider the weak decays of a B meson to final states that contain a S-wave radially excited vector meson. We consider vector-pseudoscalar final states and calculate ratios of the type $B \to ρ^{\prime} π/B \to ρπ$, $B \to ω^{\prime} π/B \to ωπ$ and $B \to ϕ^{\prime} π/B \to ϕπ$ where $ρ^{\prime}$, $ω^{\prime}$ and $ϕ^{\prime}$ are higher $ρ$, $ω$ and $ϕ$ S-wave radial excitations. We find such decays to have larger or similar branching ratios compared to decays where the final state $ρ$, $ω$ and $ϕ$ are in the ground state. We also study the effect of radial mixing in the vector system generated from hyperfine interaction and the annihilation term.
We discuss the seemingly contradictory constraints of simultaneously preserving the SU(3)-symmetric Cabibbo description of the weak vector baryon matrix elements, accounting for SU(3) flavor symmetry breaking and describing the observed violation of the Gottfried Sum Rule. We try to construct a simple model that will satisfy these constraints and use it to explain the generic difficulties and tradeoffs.
The two body decays of $B_d$ and $B_s$ decays into $J/ψM$, where $M$ is a light meson, is studied under the very simple assumptions that the spectator quark does not play a role in the decay of the weak heavy quark or antiquark. This hypothesis leads to interesting relations between decay amplitudes. The assumption of SU(3) symmetry leads to additional relations between the decay amplitudes and in particular, the eight CP eigenstates $J/ψK_S$, $J/ψη$, $J/ψη^{\prime}$ and $J/ψπ^o$ are all given in terms of 0. If agreement with experiment validates these assumptions the parameters over determined by the results will give information about the ratio of penguin to tree contributions to the "golden channel" $B^o \to J/ψK_S$ decay and will provide tests for the standard $η-η^{\prime}$ mixing, which assumes that this mixing is determined by a single mixing angle, as well as determine the value of the mixing angle. We also present tests of the standard $η-η^{\prime}$ mixing involving semileptonic $D$ decays.