arXiv subjects

Isard Dunietz

Publications and source records attributed to Isard Dunietz.

At least 19 recordsLinked to original sources

arXiv2001

In Pursuit of New Physics with B_s Decays

The presence of a sizeable CP-violating phase in B_s^0-B_s^0-bar mixing would be an unambiguous signal of physics beyond the Standard Model. We analyse various possibilities to detect such a new phase considering both tagged and untagged decays. The effects of a sizeable width difference Delta Gamma between the B_s mass eigenstates, on which the untagged analyses rely, are included in all formulae. A novel method to find this phase from simple measurements of lifetimes and branching ratios in untagged decays is proposed. This method does not involve two-exponential fits, which require much larger statistics. For the tagged decays, an outstanding role is played by the observables of the time-dependent angular distribution of the B_s -> J/psi [-> l^+ l^-] ϕ[-> K^+K^-] decay products. We list the formulae needed for the angular analysis in the presence of both a new CP-violating phase and a sizeable Delta Gamma, and propose methods to remove a remaining discrete ambiguity in the new phase. This phase can therefore be determined in an unambiguous way.

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arXiv2000

Improved Methods for Observing CP Violation in B+/- --> K+/- D0 and Measuring the CKM Phase gamma

Various methods are discussed for obtaining the CKM angle gamma through the interference of the charged B-meson decay channels B- -> K- D0 and B- -> K- D0-bar where the D0 and D0-bar decay to common final states. It is found that choosing final states which are not CP eigenstates can lead to large direct CP violation which can give significant bounds on gamma without any theoretical assumptions. If two or more modes are studied, gamma may be extracted with a precision on the order of +/-15 degrees given about 10^8 B-mesons. We also discuss the case of three body decays of the D0 where additional information may be obtained from the distribution of the D0 decay products and consider the impact of D-D-bar oscillations.

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arXiv2000

On determining CKM angles alpha and beta

Because the Bd -> J/psi Ks asymmetry determines only sin(2 beta), a discrete ambiguity in the true value of beta remains. This note reviews how the ambiguity can be removed. Extractions of the CKM angle alpha are discussed next. Some of the methods require very large data samples and will not be feasible in the near future. In the near future, semi-inclusive CP-violating searches could be undertaken, which are reviewed last.

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arXiv1998

CP Asymmetries in (Semi-)Inclusive B0 Decays

It was recently pointed out that inclusive B^0(t) decays could show CP violation. The totally inclusive asymmetry is expected to be tiny [O(10^{-3})] because of large cancellations among the asymmetries in the charmless, single charm and double charm final states. Enriching particular final state configurations could significantly increase the CP-asymmetry and observability. Such studies can extract fundamental CKM (Cabibbo-Kobayashi-Maskawa) parameters, and (perhaps) even Delta m(B_s). A superb vertex detector could see CP violation with 10^5 (10^6) flavor-tagged B_s (B_d) mesons within the CKM model. Because the effects could be significantly larger due to new physics, they should be searched for in existing or soon available data samples.

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arXiv1998

Heavy Baryon Production and Decay

The branching ratio B(Lambda_c -> p K- pi+) normalizes the production and decay of charmed and bottom baryons. At present, this crucial branching ratio is extracted dominantly from B.bar -> baryons analyses. This note questions several of the underlying assumptions and predicts sizable B.bar -> D(*) N N'.bar X transitions, which were traditionally neglected. It predicts B(Lambda_c -> p K- pi+) to be significantly larger (0.07 +/- 0.02) than the world average. Some consequences are briefly mentioned. Several techniques to measure B(Lambda_c -> p K- pi+) are outlined with existing or soon available data samples. By equating two recent CLEO results, an appendix obtains B(D0 -> K- pi+)= 0.035 +/- 0.002, which is somewhat smaller than the current world average.

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arXiv1998

Extracting CKM Phases and $B_s - \bar{B}_s$ Mixing Parameters from Angular Distributions of Non-Leptonic B Decays

Suggestions for efficiently determining the lifetimes and mass difference of the light and heavy $B_s$ mesons ($B_s^L, B_s^H$) from $B_s \to J/ ψϕ, D_s^{*+}D_s^{*-}$ decays are given. Using appropriate weighting functions for the angular distributions of the decay products (moment analysis), one can extract $(Γ_H, Γ_L, Δm)_{B_s}$. Such a moment analysis allows the determination of the relative magnitudes and phases of the CP-odd and CP-even decay amplitudes. Efficient determinations of CP-violating effects occuring in $B_s \to J/ψϕ, D_s^{*+} D_s^{*-}$ are discussed in the light of a possible width difference $(ΔΓ)_{B_s}$, and the utility of this method for $B \to J/ψK^*, D^{\ast +}_s \bar D^{\ast}$ decays is noted. Since our approach is very general, it can in principle be applied to all kinds of angular distributions and allows the determination of all relevant observables, including fundamental CKM (Cabibbo-Kobayashi-Maskawa) parameters, as well as tests of various aspects of the factorization hypothesis. Explicit angular distributions and weighting functions are given, and the general method that can be used for any angular distribution is indicated.

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arXiv1998

Resolving a Discrete Ambiguity in the CKM Angle $β$ through $B_{u,d} \to J/ψK^\ast$ and $B_s \to J/ψϕ$ Decays

It is well known that $\sin(2β)$, where $β$ is one of the angles of the unitarity triangle of the CKM matrix, can be determined in a theoretically clean way by measuring mixing-induced CP violation in the decay $B_d \to J/ψK_S$. Another clean extraction of this CKM angle is provided by the time-dependent angular distribution for the decay products of $B_d \to J/ψ(\to l^+l^-) K^{\ast0}(\to π^0 K_S)$, where we have more observables at our disposal than in the case of $B_d \to J/ψK_S$, so that in addition to $\sin(2β)$ also $\cos(2β)$ can be probed in a direct way. Unfortunately a sign ambiguity remains in $\cos(2β)$. If it could be resolved, a discrete ambiguity in the extraction of the CKM angle $β$ could be resolved as well, which would allow a more incisive test of the CKM model of CP violation. This note shows that detailed time-dependent studies of $B_{u,d} \to J/ψK^{\ast}$ and $B_s \to J/ψϕ$ decay processes can determine the sign of $\cos(2β)$, thereby removing the corresponding ambiguity in the extraction of the CKM angle $β$.

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arXiv1997

Clean CKM Information from Bd(t) -> D(*)+/- pi-/+

It has been known for many years that the Bd(t) -> D(*)+/- {pi-/+, rho-/+, a1-/+} modes may involve observable CP violating effects. This note describes how to determine cleanly the Cabibbo-Kobayashi-Maskawa (CKM) phase phi = -2 beta - gamma = -pi + alpha - beta, even in the presence of possible final state interactions. A discrete ambiguity remains.

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arXiv1997

Beautiful CP Violation

CP violation is observed to date only in K^0 decays and is parameterizable by a single quantity epsilon. Because it is one of the least understood phenomena in the Standard Model and holds a clue to baryogenesis, it must be investigated further. Highly specialized searches in K^0 decays are possible. Effects in B decays are much larger. In addition to the traditional B_d -> J/ψK_S, pi^+pi^- asymmetries, CP violation could be searched for in already existing inclusive B data samples. The rapid B_s - B_s.bar oscillations cancel in untagged B_s data samples, which therefore allow feasibility studies for the observation of CP violation and the extraction of CKM elements with present vertex detectors. The favored method for the extraction of the CKM angle gamma is shown to be unfeasible and a solution is presented involving striking direct CP violation in charged B decays. Novel methods for determining the B_s mixing parameter Delta m are described without the traditional requirement of flavor-specific final states.

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arXiv1997

Enhanced Charmless Yield in B Decays and Inclusive B-Decay Puzzles

Our analysis suggests that the charmless yield in B decays is enhanced over traditional estimates. The c c.bar pair produced in b to c c.bar transitions may be seen significantly as light hadrons due to non-perturbative effects. Existing data samples at Upsilon(4S) and Z^0 factories allow key measurements which are outlined.

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arXiv1997

Large Charmless Yield in B Decays and Inclusive B Decay Puzzles

In recent studies of inclusive $B$ decays, it has been suggested that either $B$ mesons decay much more copiously to final states with no open charm than currently assumed, or $B(D^0 \to K^-π^+)$ has to be reduced significantly. This note takes the experimental $B(D^0 \to K^-π^+)$ at its face value and estimates $B(b\to$ no open charm) using complementary methods: one accounts for the $c$ quark in $b\to c$ transitions, the other accounts for the $\bar c$ quark in $b\to c\bar c s$ transitions. Through cancellation of errors, the average gives our best estimate of $B(b\to$ no open charm), and the difference measures the consistency. The results of the methods are consistent with each other, strongly suggesting a much enhanced $B(b\to$ no open charm). This observation indicates that non-perturbative QCD effects are probably causing a sizable fraction of the $b\to c\bar cs$ transitions to be seen as charmless $b\to s$ processes, contrary to smaller traditional expectations. This mechanism has generally been overlooked and may explain the existing experimental data within the framework of the standard model. We then briefly discuss implications on baryon production governed by $b\to c\bar cs$ processes, rare hadronic $B$ decays and CP violation studies.

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arXiv1996

Enhanced CP Violation with $B\to K D^0 (\overline D^0)$ Modes and Extraction of the CKM Angle gamma

The Gronau-London-Wyler (GLW) method extracts the CKM angle $γ$ by measuring $B^\pm$ decay rates involving $D^0/\overline D^0$ mesons. Since that method necessitates the interference between two amplitudes that are significantly different in magnitude, the resulting asymmetries tend to be small. CP violation can be greatly enhanced for decays to final states that are common to both D^0 and $\overline D^0$ and that are not CP eigenstates. In particular, large asymmetries are possible for final states f such that $D^0\to f$ is doubly Cabibbo suppressed while $\overline D^0\to f$ is Cabibbo allowed. The measurement of interference effects in two such modes allows the extraction of $γ$ without prior knowledge of $Br(B^-\to K^- \overline D^0)$, which may be difficult to determine due to backgrounds.

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arXiv1996

A Way to Measure Very Large Δm for B_s Mesons

While present vertex technology cannot measure x_s much beyond 20, the Standard Model accomodates significantly larger x_s values. This note presents a method to determine very large x_s with present technology. The determination is based upon subtle coherence effects between initial B_s mesons and daughter neutral kaons, discovered by one of us several years ago. The method may be useful also for measuring very small width or mass differences in mixed neutral B or D mesons.

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arXiv1996

Mixing-induced CP Asymmetries in Inclusive $B$ Decays

We consider CP violating asymmetries that are induced by particle-antiparticle mixing in inclusive channels of neutral $B$ meson decay. Not only are the branching ratios sizable, at the 1% to 50% level, but some of those asymmetries are expected to be large because of substantial CKM phases. The inclusive sum partially dilutes the asymmetries, but the dilution factor is calculable, assuming local quark-hadron duality, and CKM parameters can be reliably extracted. We discuss in detail the determination of $sin 2α$ from charmless final states in decays of $B_d$ mesons and survey the asymmetries for other inclusive final states. While probably not yet sensitive to standard model predictions, meaningful CP violation studies can be conducted with existing data samples of inclusive neutral $B$ decays.

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arXiv1996

Comments on Recent Measurements of R_c and R_b

Discrepancies between Standard Model predictions and experimental measurements of the fractions R_c and R_b of hadronic Z decays to charm and bottom are investigated. We show that there exists a discrepancy in two complementary determinations of B(Bbar --> D X). Reducing the branching ratio B(D0 --> K- Pi+) by about 15% from currently accepted values to 3.50+/-0.21 removes the discrepancy. Since B(D0 --> K- Pi+) calibrates most charmed hadron yields, the reduced value also eliminates the discrepancy between the predicted and measured values of R_c and mitigates a problem in semileptonic B decays. A reduction in B(D0 --> K- Pi+) would also mean that roughly 15% of all D0 and D+ decays have not been properly taken into account. It is shown that if the missing decay modes involve multiple charged particles, they would be more likely to pass the requirements for lifetime B tagging at LEP and SLC. This would mean that the charm tagging efficiency in (Z --> c cbar) has been underestimated. As a consequence R_b would need to be revised downward, potentially bringing it in line with the Standard Model prediction.

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arXiv1996

On the Necessity of Recalibrating Heavy Flavor Decays and its Impact on Apparent Puzzles in High Energy Physics

It is demonstrated that charm is systematically undercounted in various experiments. Via a process of elimination, $B(D^0 \rightarrow K^- π^+ )$ is identified as the culprit. It calibrates essentially all charmed meson production and decay properties, and thus is central to the physics of heavy flavors. We predict it to decrease significantly below currently accepted values. We suggest several novel methods for precise measurements of $B(D^0 \rightarrow K^- π^+ )$. The $B(Λ_c \rightarrow pK^-π^+)$, on the other hand, calibrates heavy-flavored baryons. Its world average relies heavily on a model of baryon production in $B$ decays, which would be invalidated if $\overline B\rightarrow D^{(*)} \stackrel{(-)}{N} X$ processes were found to be significant. A Dalitz-plot analysis explains naturally the soft inclusive $Λ_c$ momentum spectrum in $\overline B$ decays, and predicts sizable $\overline B\rightarrow D^{(*)}\stackrel{(-)}{N} X$ processes. Consistently carrying through these modifications to charmed meson and baryon yields has the potential to resolve the heavy-flavor puzzles at $Z^0$-factories [$R_c,\; R_b$], the number of charm per $B$-decay puzzle, and the semi-leptonic $B$ decay puzzles. We emphasize that state of the art theoretical calculations are consistent with precise experimental measurements regarding $B(\overline B\rightarrow X\ell\barν)$. Recent CLEO measurements are interpreted as newly available cross-checks that any inclusive theoretical investigation must satisfy. Another topic of this report concerns the $b\rightarrow c + \overline D^{(*)}\overline K$ transitions, which were predicted to be sizable and subsequently confirmed by CLEO. This report discusses the underlying dynamics of those processes and quantifies the necessary modifications in existing

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arXiv1996

CP violation and the CKM angle $γ$ from angular distributions of untagged $B_s$ decays governed by $\bar b\to\bar c u\bar s$

We demonstrate that time-dependent studies of angular distributions for $B_s$ decays caused by $\bar b\to\bar cu\bar s$ quark-level transitions extract cleanly and model-independently the CKM angle $γ$. This CKM angle could be cleanly determined from untagged $B_s$ decays alone, if the lifetime difference between the $B_s$ mass eigenstates $B_s^L$ and $B_s^H$ is sizable. The time-dependences for the relevant tagged and untagged observables are given both in a general notation and in terms of linear polarization states and should exhibit large CP-violating effects. These observables may furthermore provide insights into the hadronization dynamics of the corresponding exclusive $B_s$ decays thereby allowing tests of the factorization hypothesis.

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arXiv1996

CP violation and CKM phases from angular distributions for $B_s$ decays into admixtures of CP eigenstates

We investigate the time-evolutions of angular distributions for $B_s$ decays into final states that are admixtures of CP-even and CP-odd configurations. A sizable lifetime difference between the $B_s$ mass eigenstates allows a probe of CP violation in time-dependent untagged angular distributions. Interference effects between different final state configurations of $B_s\to D^{*+}_s D^{*-}_s$, $J/ψϕ$ determine the Wolfenstein parameter $η$ from untagged data samples, or -- if one uses $|V_{ub}|/|V_{cb}|$ as an additional input -- the notoriously difficult to measure CKM angle $γ$. Another determination of $γ$ is possible by using isospin symmetry of strong interactions to relate untagged data samples of $B_s\to K^{\ast+} K^{\ast-}$ and $B_s\to K^{\ast0} \overline{K^{\ast0}}$. We note that the untagged angular distribution for $B_s\toρ^0 ϕ$ provides interesting information about electroweak penguins.

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