arXiv subjects

Harry J. Lipkin

Publications and source records attributed to Harry J. Lipkin.

At least 37 records · Page 2Linked to original sources

arXiv2007

The New Sigma_b multiplet, heavy baryon mass predictions, meson-baryon universality and magnetic moments of Lambda_c and Lambda_b

The recent measurement by CDF M(Sigma_b)-M(Lambda_b)=192 MeV is in striking agreement with our theoretical prediction M(Sigma_b)-M(Lambda_b) = 194 MeV. In addition, the measured splitting M(Sigma_b*)-M(Sigma_b) = 21 MeV agrees well with the predicted splitting of 22 MeV. We point out the connection between these predictions and an effective supersymmetry between mesons and baryons related by replacing a light antiquark by a light diquark. We discuss the theoretical framework behind these predictions and use it to provide additional predictions for the masses of spin-1/2 and spin-3/2 baryons containing heavy quarks, as well as magnetic moments of Lambda_b and Lambda_c.

hep-ph↗

arXiv2007

Predictions for masses of bottom baryons

The recent observation of Sigma_b^{+-} (uub and ddb) and Xi_b^- (dsb) baryons at the Tevatron within 2 MeV of our theoretical predictions provides a strong motivation for applying the same theoretical approach, based on modeling the color hyperfine interaction, to predict the masses of other bottom baryons which might be observed in the foreseeable future. For S-wave qqb states we predict M(Omega_b) = 6052.1+-5.6 MeV, M(Omega^*_b) = 6082.8+-5.6 MeV, and M(Xi_b^0) = 5786.7 +- 3.0 MeV. For states with one unit of orbital angular momentum between the b quark and the two light quarks we predict M(Lambda_{b[1/2]}) = 5929+-2 MeV, M(Lambda_{b[3/2]}) = 5940+-2 MeV, M(Xi_{b[1/2]}) = 6106+-4 MeV, and M(Xi_{b[3/2]}) = 6115+-4 MeV.

hep-ph↗

arXiv2007

Predictions for masses of Xi_b baryons

The recent observation by CDF of Sigma_b^{+-} (uub and ddb) baryons within 2 MeV of the predicted Sigma_b - Lambda_b splitting has provided strong confirmation for the theoretical approach based on modeling the color hyperfine interaction. We now apply this approach to predict the masses of the Xi_b family of baryons with quark content usb and dsb - the ground state Xi_b at 5790 to 5800 MeV, and the excited states Xi_b^' and Xi_b^*. The main source of uncertainty is the method used to estimate the mass difference m_b - m_c from known hadrons. We verify that corrections due to the details of the interquark potential and to Xi_b-Xi_b^' mixing are small.

hep-ph↗

arXiv2007

New systematics in charmless strange $B^+ \to VP$ decays

Latest data on charmless strange vector-pseudoscalar $B^+$ decays now including $B^+\to ρ^+ K^o$ confirm a simple penguin model in which the gluon $G$ in an initial $\bar s u G$ state fragments equally into $u \bar u$, $d \bar d$ and $s \bar s$ and all form factors are equal. A search for possible additional contributions shows only a few signals not obscured by experimental errors whose implications are discussed. The experimental value of $0.25 \pm 0.11$ for the ratio of the branching ratios $BR(B^+ \to K^{*+}η)$ to $BR(B^+\to K^{*+}η')$ confirms the parity selection rule prediction 0.32. Large violations arise in a new sum rule for the sum of these branching ratios, analogous to the similar pseudoscalar sum rule including $K^+η$ and $K^+η'$. Indications for either an electroweak penguin contribution or additional admixtures like instrinsic charm in the $η-η'$ system remain to be clarified. An alternative symmetry description with new predictive power clarifies the simple penguin approximation and presents new predictions which can be tested experimentally. The fragmentation of the $\bar s u G$ state into two mesons is described by a strong interaction S-matrix dominated by nonexotic hadron resonances in multiparticle intermediate states.

hep-ph↗

arXiv2007

New Quark Relations for Hadron Masses and Magnetic Moments - A Challenge for Explanation from QCD

Prompted by the recent surprising results in QCD spectroscopy, we extend the treatment of the constituent quark model showing that mass differences and ratios have the same values when obtained from mesons and baryons. We obtain several new successful relations involving hadrons containing two and three strange quarks and hadrons containing heavy quarks and give a new prediction regarding spin splitting between doubly charmed baryons. We provide numerical evidence for an effective supersymmetry between mesons and baryons related by replacing a light antiquark by a light diquark. We also obtain new relations between quark magnetic moments and hadron masses. Limits of validity of this approach and disagreements with experiment in properties of the Sigma and Xi baryons are discussed as possible clues to a derivation from QCD.

hep-ph↗

arXiv2007

Exotic Hadrons in the Constituent Quark Model

Exotic hadrons are important because their existence or absence can provide important clues to understanding how QCD makes hadrons from quarks and gluons. The first experimentally confirmed exotic will be the first hadron containing both $qq$ and $\bar q q$ pairs and the first hadron containing color sextet and color octet pairs. Theoretical models are not very useful because there is no accepted model for multiquark systems with color-space correlations. The constituent quark model is the only phenomenological model with predictive power that has given experimentally tested universal predictions for both mesons and baryons. This paper reviews its explanation for why there are no bound exotics and its guidance to the search for heavy-flavored exotic tetraquarks and pentaquarks. A possible supersymmetry between mesons and baryons leading to meson-baryon mass relations not easily obtained otherwise is discussed.

hep-ph↗

arXiv2007

From Sakata Model to Goldberg-Ne'eman Quarks and Nambu QCD Phenomenology and "Right" and "Wrong" experiments

The basic theoretical milestones were the Sakata SU(3) symmetry, the Goldberg-Ne'eman composite model with SU(3) triplets having baryon number (1/3) and the Nambu color gauge Lagrangian. The transition was led in right and wrong directions by experiments interpreted by phenomenology. A "good" experiment on $\bar p p$ annihilation at rest showed that the Sakata model predictions disagreed with experiment. A "bad" experiment prevented the use of the Goldberg-Ne'eman triplet model to predict the existence and masses of the of the $Ξ^*$ and $Ω^-$. More "good" experiments revealed the existence and mass of the $Ξ^*$ and the $Ω^-$ and the absence of positive strangeness baryon resonances, thus confirming the "tenfold way". Further "good experiments" revealed the existence of the vector meson nonet, SU(3) breaking with singlet-octet mixing and the suppression of the $ϕ\to ρπ$ decay. These led to the quark triplet model. The paradox of peculiar statistics then arose as the $Δ^{++}$ and $Ω^-$ contained three identical spin-1/2 fermions coupled symmetrically to spin (3/2). This led to color and the Nambu QCD. The book "Lie Groups for Pedestrians" used the Sakata model with the name "sakaton" for the $pnΛ$ triplet to teach the algebra of SU(3) to particle physicists in the U.S. and Europe who knew no group theory. The Sakata model had a renaissance in hypernuclear physics in the 1970's.

hep-ph↗

arXiv2006

Quantum Theory of Neutrino Oscillations for Pedestrians - Simple Answers to Confusing Questions

Why are different mass states coherent? What is the correct formula for the oscillation phase? How can textbook formulas for oscillations in time describe experiments which never measure time? How can we treat the different velocities and different transit times of different mass eigenstates and avoid incorrect factors of two? How can textbook forumulas which describe coherence between energy states be justified when Stodolsky's theorem states there is no coherence between different energies? Is covariant relativistic quantum field theory necessary to describe neutrino oscillations? How important is the detector, which is at rest in the laboratory and cannot be Lorentz tranformed to other frames? These questions are answered by a simple rigorous calculation which includes the quantum fluctuations in the position of the detector and in the transit time between source and detector. The commonly used standard formula for neutrino oscillation phases is confirmed. An "ideal" detector which measures precisely the energy and momentum of the neutrino destroys all phases in the initial wave packet and cannot observe oscillations. A realistic detector preserves the phase differences between neutrinos having the same energy and different momenta and confirms the standard formula. Whether phase differences between neutrinos with different energies are observable or destroyed by the detector is irrelevant.

hep-ph↗

arXiv2006

CP violation difference in $B^o$ and $B^\pm$ decays explained No tree-penguin interference in $B^+ \to K^+π^o$

A new experimental analysis of $B\to Kπ$ decays provides finite experimental values for the contributions from interference terms between the dominant penguin amplitude and the color-favored and color-suppressed tree amplitudes. These results can explain the puzzling failure to see CP violation in $B^\pm\to Kπ$ decays. Tree-penguin interference contributions are commonly believed to be the source of the observed direct CP violation in $B^o\to K^\pmπ^\mp$ decays. The data show that the color-favored and color-suppressed tree contributions interfere destructively in $B^\pm\to K^\pmπ^o$ decays and nearly cancel. This suprising cancellation is not predicted by present theory. There is also no prediction for any difference produced by changing the flavor of the spectator quark. Isospin and Pauli effects that change with spectator quark flavor are examined and show using group theory and the color-spun SU(6) algebra how they produce both the near cancellation and the dependence on spectator quark flavor. The standard $B\to Kπ$ analysis which treats tree-penguin interference only in first order has three parameters overdetermined by four experimental branching ratios. Previous analyses confirmed the model but with large errors leaving the values of tree-penguin interference contributions less that two standard deviations from zero. The new analysis finds interference contributions well above the errors.

hep-ph↗

arXiv2006

A tetraquark model for the new X(1576) K+ K- resonance

We discuss the likely tetraquark interpretation of the X(1576) K+ K- isovector resonance recently reported by BES with J^{PC}=1^{--}. We point out that if this interpretation as a four-quark state is correct, the (s u sbar dbar) tetraquark decays might have striking signatures. We also provide predictions for possible analogous tetraquarks involving heavy quarks - (c q cbar qbar) and (b q bbar qbar).

hep-ph↗

arXiv2006

Diquarks and antiquarks in exotics: a menage a trois and a menage a quatre

A menage a trois is very different from an ordinary family. Similarly, exotic hadrons with both qq and qbar q pairs have important color-space correlations that are completely absent in ordinary mesons and baryons. The presence of both types of pairs requires attention to the basic QCD physics that the q qbar interaction is much stronger than the qq interaction. This new physics in multiquark systems produces color structures totally different from those of normal hadrons, for example the ud system is utterly unlike the ud diquark in the uds Lambda baryon. The color-space correlations produce unusual experimental properties in tetraquarks with heavy quark pairs which may be relevant for newly discovered mesons like the X(3872) resonance. Tetraquark masses can be below the two-meson threshold for sufficiently high quark masses. A simple model calculation shows the b q bbar ubar and b q cbar qbar tetraquarks below the B Bbar and B Dbar thresholds. Some of these states have exotic electric charge and their decays might have striking signatures involving monoenergetic photons and/or pions.

hep-ph↗

arXiv2006

Bounds on Localized Modes in the Crystal Impurity Problem

Using general properties of the crystal site representation normal mode matrix, we provide some very simple bounds on localized modes in simple, body-centered and face-centered cubic crystals with substitutional point defects. We derive a trace condition constraint on the net change in crystal eigenfrequencies caused by the introduction of a defect, with the condition being a completely general one which holds for any combination of central and non-central crystal force-constants and for all-neighbor interactions. Using this condition we show that the sufficient condition for producing localized modes in an arbitrary cubic crystal by a mass change at the defect site is that the defect mass be less than one half of that of the host atom mass which it replaces, and that the sufficient condition for producing localized modes in an arbitrary cubic crystal by force-constant changes alone is that the defect site self force-constant be greater than twice that of the pure crystal self force-constant of the host atom which it replaces.

cond-mat.other↗

arXiv2005

Analysis of new charmless strange B decay data leaves high $B\to Kη'$ and $B\to Kη' X$ still unexplained

The question of whether the anomalously large $B \to Kη' $ and $B \to Kη' X $ (inclusive) branching ratios are consistent with the standard model or a sign of new physics is still open and in the experimental court. The nature of the extra hadron $X$ in $B \to Kη' X $ is completely unknown. Directions for investigation and analysis of inclusive data are suggested as well as for comparable inclusive data on $B \to KηX $. New data confirming the prediction $BR(K^\pm ρ^o) = BR(K^\pm ω)$ support flavor-topology $B \to VP$ sum rules based on the OZI rule and emphasize the sharp contrast with the failure of the analogous $B \to PP $ sum rule due to the anomalously large $BR(B \to Kη')$. Confirmation of OZI validity in B-decay analyses for VP final states suggests improving data on the analogous neutral decay difference $BR(B^o \to K^o ρ^o) - BR(B^o \to K^o ω)$ which measures tree-penguin interference and possible direct CP violation. A successful approximate isospin sum rule is rearranged and reinterpreted to pinpoint tree-penguin interference in $B \to K π$ and $B \to K ρ$ transitions. The magnitude of the interference is shown to still be at the statistical noise level with present data.

hep-ph↗

arXiv2005

Isospin Analysis of pentaquark production forbids gamma p --> Theta^+ K_s and allows gamma n --> Theta^+ K^-

The discrepancy between Theta^+ photoproduction on proton vs. deuteron can be resolved if the photon couples much more strongly to K^+K^- than to K0 K0bar as indicated by the experimentally observed asymmetry between gamma p --> Lambda(1520) K^+ and gamma n --> Lambda(1520) K_s. Significant signal-background interference effects can occur in experiments like gamma N --> Kbar Theta^+ which search for the Theta^+ as a narrow I=0 resonance in a definite final state against a nonresonant background, with an experimental resolution coarser than the expected resonance width. We show that when the signal and background have roughly the same magnitude, destructive interference can easily combine with a limited experimental resolution to completely destroy the resonance signal. Whether or not this actually occurs depends critically on the yet unknown relative phase of the I=0 and I=1 amplitudes. We discuss the implications for some specific experiments.

hep-ph↗

arXiv2005

Is observed direct CP violation in $B_d \to K^+ π^-$ due to new physics? Check standard model prediction of equal violation in $B_s \to K^- π^+$

The recently observed direct CP violation in $B_d \to K^+ π^-$ has raised suggestions of possible new physics. A robust test of the standard model vs. new physics is its prediction of equal direct CP violation in $B_s \to K^- π^+$ decay. CPT invariance requires the observed CP violation to arise from the interference between the dominant penguin amplitude and another amplitude with a different weak phase and a different strong phase. The penguin contribution to $B_d \to K^+ π^-$ is known to be reduced by a CKM factor in $B_s \to K^- π^+$. Thus the two branching ratios are very different and a different CP violation is expected. But in the standard model a miracle occurs and the interfering tree diagram is enhanced by the same CKM factor that reduces the penguin to give the predicted equality. This miracle is not expected in new physics; thus a search for and measurement of the predicted CP violation in $B_s \to K^- π^+$ decay is a sensitive test for a new physics contribution. A detailed analysis shows this prediction to be robust and insensitive to symmetry breaking effects and possible additional contributions.

hep-ph↗

arXiv2005

On a possible tetraquark cousin of the Theta^+

If a narrow Theta^+ pentaquark exists, it is likely that a ud\bar s-ud triquark-diquark configuration is a significant component of its wave function. If so, the mechanism responsible for the binding of a triquark and a diquark is also likely to bind the triquark to an \bar s antiquark. We discuss the expected properties of such a ud\bar s-\bar s tetraquark meson. In particular, we point out that for a 0^+ isoscalar ud\bar s\bar s meson the lowest allowed decay mode is a four-body K K pi pi channel with a small phase space and a distinctive experimental signature.

hep-ph↗

arXiv2005

New tests for experiments producing pentaquarks

The distribution of the squared momentum difference |P_A|^2 - |P_B|^2 between the momenta in the laboratory system of two experimentally observed particles A and B provides a test for whether an observed mass peak indicates a real resonance rather than nonresonant background or kinematic reflection. The angular distribution of the relative momenta in the center-of-mass system exhibits a forward-backward symmetry in the production and decay of any resonance with a definite parity. This symmetry is not expected in other nonresonant processes and can be expressed without needing angular distributions in terms of the easily measured momenta in the laboratory frame that are already measured and used to calculate the invariant mass of the system. Our test is especially useful for low statistics experiments where the full angular distribution cannot be determined. It can be applied to both fixed-target and collider searches for the Theta^+ and Theta_c pentaquarks.

hep-ph↗

arXiv2005

Why pentaquarks are seen in some experiments and not in others

The $Θ^+$ Pentaquark is a Very narrow $Γ\approx 1$ MeV KN Resonance. Why do some experiments see it and others do not? The lowest quark configuration that can describe it is exotic $uudd \bar s$. Why have no exotics been seen before? Is this the beginning of a new spectroscopy? Can it help toteach us about How QCD makes hadrons from quarks and gluons?

hep-ph↗