arXiv subjects

Ivan Maksymyk

Publications and source records attributed to Ivan Maksymyk.

8 recordsLinked to original sources

arXiv2014

Beyond S, T and U

The contribution to precision electroweak measurements due to TeV physics which couples primarily to the $W^\pm$ and $Z$ bosons may be parameterized in terms of the three `oblique correction' parameters, S, T and U. We extend this parameterization to physics at much lower energies, $\ge 100$ GeV, and show that in this more general case three more parameters are required (which we call V, W and X). Only two of these appear in neutral-current experiments, while the third new parameter enters into the $W^\pm$ width.

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arXiv1999

Realistic Anomaly-mediated Supersymmetry Breaking

We consider supersymmetry breaking communicated entirely by the superconformal anomaly in supergravity. This scenario is naturally realized if supersymmetry is broken in a hidden sector whose couplings to the observable sector are suppressed by more than powers of the Planck scale, as occurs if supersymmetry is broken in a parallel universe living in extra dimensions. This scenario is extremely predictive: soft supersymmetry breaking couplings are completely determined by anomalous dimensions in the effective theory at the weak scale. Gaugino and scalar masses are naturally of the same order, and flavor-changing neutral currents are automatically suppressed. The most glaring problem with this scenario is that slepton masses are negative in the minimal supersymmetric standard model. We point out that this problem can be simply solved by coupling extra Higgs doublets to the leptons. Lepton flavor-changing neutral currents can be naturally avoided by approximate symmetries. We also describe more speculative solutions involving compositeness near the weak scale. We then turn to electroweak symmetry breaking. Adding an explicit μterm gives a value for Bμthat is too large by a factor of order 100. We construct a realistic model in which the μterm arises from the vacuum expectation value of a singlet field, so all weak-scale masses are directly related to m_{3/2}. We show that fully realistic electroweak symmetry breaking can occur in this model with moderate fine-tuning.

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arXiv1997

Comment Concerning Relativistic Corrections in NRQCD

We examine the subtle differences between two possible frameworks for the calculation of quarkonium production. The differences between the two methods are not a concern when one calculates only to leading order in the relativistic expansion, but when relativistic corrections are included, the two formulations seem at first to be at variance with one another. They can be reconciled however via a relativistically corrected mass relation relating the boundstate mass and the quark mass.

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arXiv1997

Photoproduction of J/$ψ$ in the forward region

We study the phenomenology of fixed-target elastic $J/ψ$ photoproduction in the NRQCD factorization formalism. Our the goal is to test an essential feature of this formalism --- the color-octet mechanism. We obtain an order-of-magnitude estimate for a certain linear combination of NRQCD color-octet matrix elements. Our estimate is consistent with other empirical determinations and with the $v$-scaling rules of NRQCD.

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arXiv1996

NRQCD matrix elements in polarization of J-Psi produced from b-decay

We present the non-relativistic QCD (NRQCD) prediction for the polarization of the J-Psi produced in b to J-Psi + X, as well as the helicity-summed production rate. We propose that these observables provide a means of measuring the three most important color-octet NRQCD matrix elements involved in J-Psi production. Anticipating the measurement of the polarization parameter alpha, we determine its expected range given current experimental bounds on the color-octet matrix elements.

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arXiv1995

Hadronic $ψ$ production calculated in the NRQCD factorization formalism

The NRQCD factorization formalism of Bodwin, Braaten, and Lepage prescribes how to write quarkonium production rates as a sum of products of short-distance coefficients times non-perturbative long-distance NRQCD matrix elements. We present, in the true spirit of the factorization formalism, a detailed calculation of the inclusive cross section for hadronic $ψ$ production. We find that in addition to the well known {\it color-singlet} production mechanisms, there are equally important mechanisms in which the $c\bar{c}$ pair that forms the $ψ$ is initially produced in a {\it color-octet} state, in either a ${}^3S_1$, ${}^1S_0$, ${}^3P_0$ or ${}^3P_2$ angular-momentum configuration. In our presentation, we emphasize the ``matching'' procedure, which %is the method that allows us to determine the short-distance coefficients appearing in the factorization formula. We also point out how one may systematically include relativistic corrections in these calculations.

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arXiv1995

Can light Goldstone boson loops counter the `S-argument' against Technicolor?

We examine the oblique correction phenomenology of one-family Technicolor with light pseudo-Goldstone bosons. From loop calculations based on a gauged chiral lagrangian for Technicolor, we are lead to conclude that even though loops with light Goldstone bosons give a negative contribution to $S$ measured at the $Z$-pole, this effect is not sufficiently large to unambiguously counter the `S-argument' against one-family Technicolor. This result cannot be guessed \apriori, but must be explicitly calculated. Our analysis entails an extended version of the $STU$ oblique parametrization of Peskin and Takeuchi. In principle, this extended formalism ($STUVWX$) must be used when there are light new particles in loops.

hep-ph↗

arXiv1993

Bounding Anomalous Gauge-Boson Couplings

In this version we have corrected some minor errors in the tables, corrected typos, and added a reference. We have also updated our comparison with earlier workers. Figures are now included as uuencoded compressed tar files.

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