Theoretical High Energy Physics |
---|

Selected Publications by Greg Anderson |

Home ^{.}
Research ^{.}
Talks ^{.}
Physics

tensor products of the

**Authors:** G. Anderson, and T. Blazek.

NUHEP-TH-00-81.

E_6 is an attractive group for unification model building --- yet, the complexity of a rank 6 group makes it non-trivial to write down the structure of higher dimensional operators in this theory in terms of the Standard Model states. In this paper, we show the results of our computation of the Clebsch-Gordan coefficients for the products of the

27with irreducible representations of higher dimensionality:78,351,,351351', and351' .

**Authors:** G. Anderson, and T. Blazek.

*To appear in J. Math. Phys.*,
hep-ph/0006017,
NUHEP-TH-00-79.

We have computed the Clebsch-Gordan coefficients for the product (000001) x (000001), where (000001) is the adjoint 78-dimensional representation of E

_{6}. The results are presented for the dominant weights of the irreducible representations in this product. As a simple application we express the singlet operator in27 x 78 x 27barin terms of multiplets of the Standard Model gauge group.

Source Postscript References Related Work

**Authors:** G. Anderson, and T. Blazek.

*To appear in J. Math. Phys.*,
hep-ph/9912365,
NUHEP-TH-99-75.

In an effort to develop tools for grand unified model building for the Lie group E

_{6}, in this paper we present the computation of the Clebsch-Gordan coefficients for the product (100000)x(000010), where (100000) is the fundamental 27-dimensional representation of E_{6}and (000010) is its charged conjugate. The results are presented in terms of the dominant weight states of the irreducible representations in this product. These results are necessary for the group analysis of E_{6}operators involving also higher representations, which is the next step in this project. In this paper we apply the results to the construction of the operator27^{3}.

Source Postscript References Related Work

**Authors:** C. Albright,

*Report to the Fermilab Directorate.*,
hep-ex/0008064,
Fermilab-fn-692

In response to the growing interest in building a Neutrino Factory to produce high intensity beams of electron- and muon-neutrinos and antineutrinos, in October 1999 the Fermilab Directorate initiated two six-month studies. The first study, organized by N. Holtkamp and D. Finley, was to investigate the technical feasibility of an intense neutrino source based on a muon storage ring. This design study has produced a report in which the basic conclusion is that a Neutrino Factory is technically feasible, although it requires an aggressive R&D program. The second study, which is the subject of this report, was to explore the physics potential of a Neutrino Factory as a function of the muon beam energy and intensity, and for oscillation physics, the potential as a function of baseline.

Source Postscript References Related Work

**Authors:** V. Barger,

hep-ph/0003154,

We present an analysis of the discovery reach for supersymmetric particles at the upgraded Tevatron collider, assuming that SUSY breaking results in universal soft breaking parameters at the grand unification scale, and that the lightest supersymmetric particle is stable and neutral. We first present a review of the literature, including the issues of unification, renormalization group evolution of the supersymmetry breaking parameters and the effect of radiative corrections on the effective low energy couplings and masses of the theory. We consider the experimental bounds coming from direct searches and those arising indirectly from precision data, cosmology and the requirement of vacuum stability. The issues of flavor and CP-violation are also addressed. The main subject of this study is to update sparticle production cross sections, make improved estimates of backgrounds, delineate the discovery reach in the supergravity framework, and examine how this might vary when assumptions about universality of soft breaking parameters are relaxed. With 30 fb

^{-1}luminosity and one detector, charginos and neutralinos, as well as third generation squarks, can be seen if their masses are not larger than 200-250 GeV, while first and second generation squarks and gluinos can be discovered if their masses do not significantly exceed 400 GeV. We conclude that there are important and exciting physics opportunities at the Tevatron collider, which will be significantly enhanced by continued Tevatron operation beyond the first phase of Run II.

Source Postscript References Related Work

**Authors:** G. Anderson, H. Baer, C-H. Chen and X. Tata.

*Phys. Rev.***D61:**095005, 2000.
hep-ph/9903370,
NSF-ITP-97-146.

We explore the reach of luminosity upgrades of the Fermilab Tevatron collider for SU(5) supergravity models in which non-universal GUT-scale gaugino masses arise via a vacuum expectation value for the auxiliary component of a superfield that transforms as a

24,75or200dimensional representation of SU(5). This results in a different pattern of sparticle masses and mixing angles from what is expected in the minimal supergravity model (mSUGRA) with universal GUT scale gaugino masses. We find that the resulting signal cross sections, and hence the reach of the Tevatron, are sensitive to the gaugino masses at the GUT scale. In the24model, the large splitting amongst the two lightest neutralinos leads to SUSY events containing many isolated leptons, including events with a real leptonic Z boson plus jets plus missing energy signal which is visible over much of parameter space. In contrast, in the75and200models, the reach via leptonic SUSY signals is greatly reduced relative to mSUGRA, and the signal is usually visible only via the canonical missing E_{T}+jets channel.

Source Postscript References Related Work

**Authors:** G. Anderson, S.Carroll.

astro-ph/9711288,
NSF-ITP-97-146.

We propose a simple model in which the cosmological dark matter consists of particles whose mass increases with the scale factor of the universe. The particle mass is generated by the expectation value of a scalar field which does not have a stable vacuum state, but which is effectively stabilized by the rest energy of the ambient particles. As the universe expands, the density of particles decreases, leading to an increase in the vacuum expectation value of the scalar (and hence the mass of the particle). The energy density of the coupled system of variable-mass particles (``vamps'') redshifts more slowly than that of ordinary matter. Consequently, the age of the universe is larger than in conventional scenarios.

Source Postscript References Related Work

**Authors:** G. Anderson, U. Baur, M. Berger, F. Borcherding, A. Brandt,
D. Denisov (Co-Chair and Co-editor), S. Eno, T. Han, S. Keller (Co-Chair
and Co-editor), D. Khazins, T. LeCompte, J. Lykken, F. Olness, F. Paige,
R. Scalise, E. H. Simmons, G. Snow, C. Taylor, J. Womersley.

hep-ph/9710254,
FERMILAB-CONF-97/318-T.

One of the options for an accelerator beyond the LHC is a hadron collider with higher energy. Work is going on to explore accelerator technologies that would make such a machine feasible. This workshop concentrated on the physics and detector issues associated with a hadron collider with an energy in the center of mass of the order of 100 to 200 TeV.

Source Postscript References Related Work

**Authors:** Greg Anderson, Diego Castaño and Antonio Riotto.

*Physical Review* **D55**: 2950-2954 (1997),
hep-ph/9609463,
FERMILAB-PUB-96/147-T.

We quantify the extent to which naturalness is lost as experimental lower bounds on the Higgs boson mass increase, and we compute the natural upper bound on the lightest supersymmetric Higgs boson mass. We find that it would be unnatural for the mass of the lightest supersymmetric Higgs boson to saturate it's maximal upper bound. In the absence of significant fine-tuning, the lightest Higgs boson mass should lie below 120 GeV, and in the most natural cases it should be lighter than 108 GeV. For modest tan(beta), these bounds are significantly lower. Our results imply that a failure to observe a light Higgs boson in pre-LHC experiments could provide a serious challenge to the principal motivation for weak-scale supersymmetry.

Source Postscript References Related Work

**Authors:** G. Anderson (FNAL), C.H. Chen (U.C. Davis), J.F. Gunion (U.C. Davis),
J. Lykken (FNAL), T. Moroi (LBL), Y. Yamada (Wisconsin).

* Snowmass Working Group Report.*,
hep-ph/9609457.

We outline several well-motivated models in which GUT boundary conditions for SUSY breaking are non-universal. The diverse phenomenological implications of the non-universality for SUSY discovery at LEP2, the Tevatron, the LHC and the NLC are sketched.

Source Postscript References Related Work

**Authors:** J. Amundson, G. Anderson, H. Baer, J. Bagger, R.M. Barnett, C.H.
Chen, G. Cleaver, B. Dobrescu, M. Drees, J.F. Gunion, G.L. Kane, B. Kayser,
C. Kolda (IAS), J. Lykken, S.P. Martin, T. Moroi, S. Mrenna, M. Nojiri,
D. Pierce, X. Tata, S. Thomas, J.D. Wells, B. Wright, Y. Yamada.

* Report of Snowmass Supersymmetry Theory Working Group.*,
hep-ph/9609374.

We provide a mini-guide to some of the possible manifestations of weak scale supersymmetry. For each of six scenarios we provide a brief description of the theoretical underpinnings, the adjustable parameters, a qualitative description of the associated phenomenology at future colliders, and comments on how to simulate each scenario with existing event generators.

Source Postscript References Related Work

**Authors:** Greg W. Anderson, Andrei Linde and Antonio Riotto.

*Physical Review Letters* **77** (1996) 3716-3719,
hep-ph/9606416.

Fluctuations of scalar fields produced at the stage of preheating after inflation are so large that they can break supersymmetry much stronger than inflation itself. These fluctuations may lead to symmetry restoration along flat directions of the effective potential even in the theories where the usual high temperature corrections are exponentially suppressed. Our results show that nonthermal phase transitions after preheating may play a crucial role in the generation of the primordial baryon asymmetry by the Affleck-Dine mechanism. In particular, the baryon asymmetry may be generated at the very early stage of the evolution of the Universe, at the preheating era, and not when the Hubble parameter becomes of order the gravitino mass.

Source Postscript References Related Work

**Authors:** Greg W. Anderson and Diego Castaño.

*Physical Review* **D53**: 2403 (1996),
hep-ph/9509212.

Experimental searches for supersymmetry are entering a new era. As future experiments explore the mass range above the current lower bounds on superpartner masses, a failure to observe signals of superpartner production will begin to erode the central motivation for supersymmetry at the weak scale. In this article we present a detailed examination of which regions of supersymmetric parameter space are most natural and the extent to which weak-scale supersymmetry becomes unnatural if no superpartners are observed at LEP-II, the Tevatron, possible upgrades of these machines, and the LHC.

Source Postscript References Related Work

or when to give up on weak scale supersymmetry

**Authors:** Greg W. Anderson and Diego Castaño.

*Physical Review*** D52**: 1693-1700 (1995),
hep-ph/9412322.

Superpartner masses cannot be arbitrarily heavy if supersymmetric extensions of the standard model explain the stability of the gauge hierarchy. This ancient and hallowed motivation for weak scale supersymmetry is often quoted, yet no reliable determination of this upper limit on superpartner masses exists. In this paper we compute upper bounds on superpartner masses in the minimal supersymmetric model, and we identify which values of the superpartner masses correspond to the most natural explanation of the hierarchy stability. We compare the most natural value of these masses and their upper limits to the physics reach of current and future colliders. As a result, we find that supersymmetry could explain weak scale stability naturally even if no superpartners are discovered at LEP II or the Tevatron (even with the Main Injector upgrade). However, we find that supersymmetry cannot provide a complete explanation of weak scale stability, if squarks and gluinos have masses beyond the physics reach of the LHC. Moreover, in the most natural scenarios, many sparticles, for example, charginos, squarks, and gluinos, lie within the physics reach of either LEP II or the Tevatron. Our analysis determines the most natural value of the chargino (squark) ((gluino)) mass consistent with current experimental constraints is 50 (250) ((250)) GeV and the corresponding theoretical upper bound is 250 (700) ((800)) GeV.

Source, Postscript, References Related Work

**Authors:** Greg W. Anderson and Diego Castaño.

*Physics Letters*** B347**: 300-308 (1995),
hep-ph/9409419.

Fine-tuning criteria are frequently used to place upper limits on the masses of superpartners in supersymmetric extensions of the standard model. However, commonly used prescriptions for quantifying naturalness have some important shortcomings. Motivated by this, we propose new criteria for quantifying fine tuning that can be used to place upper limits on superpartner masses with greater fidelity. In addition, our analysis attempts to make explicit the assumptions implicit in quantifications of naturalness. We apply our criteria to the minimal supersymmetric extension of the standard model, and we find that the scale of supersymmetry breaking can be larger than previous methods indicate.

Source Postscript References Related Work

**Authors:** Greg W. Anderson, S. Dimopoulos, L. Hall, S. Raby, and G. Starkman.

*Physical Review*** D49**: 3660-3690 (1994),
hep-ph/9308333.

A class of supersymmetric SO(10) grand unified theories is proposed which predicts seven of the quark masses and mixing parameters. A systematic operator analysis of the most predictive such flavor sectors is performed, exploiting the full power of SO(10) to relate up and down-type quark mass matrices. The assumptions upon which the operator search and resulting predictions are based are stressed, together with a discussion of how the predictions are affected by a relaxation of some of the assumptions. The masses of the heaviest generation, m

_{t}, m_{b}and m_{tau}, are generated from a single renormalizable Yukawa interaction, while the lighter masses and the mixing angles are generated by non-renormalizable operators of the grand unified theory. The hierarchy of masses and mixing angles is thereby related to the ratio of grand to Planck scales, M_{G}/ M_{P}. An explicit realization of the origin of such an economical pattern of operators is given in terms of a set of spontaneously broken family symmetries. In the preferred models the top quark is found to be heavy: M_{t}= 180 ± 15 GeV. Predictions are also given for m_{s}, m_{s}/m_{d}, m_{u}/m_{d}, V_{cb}, V_{ub}/V_{cb}and the amount of CP violation. Stringent tests of these theories will be achieved by more precise measurements of M_{t}, V_{cb}, alpha strong and V_{ub}/V_{cb}and by measurements of CP violation in neutral B meson decays.

Source Postscript References Related Work

**Authors:** Greg W. Anderson,
S. Dimopoulos, L. Hall, and S. Raby.

*Physical Review*** D47**: 3702-3706 (1993),
hep-ph/9209250.

The fermion mass and mixing angle predictions of a recently proposed framework are investigated for large b and tau Yukawa couplings. A new allowed region of parameters is found for this large tan(beta) case. The two predictions which are substantially altered, m

_{t}and tan(beta), are displayed, including the dependence on the inputs |V_{cb}|, m_{c}, m_{b}and alpha strong. A simple restriction on this framework yields an additional prediction, for |V_{cb}|. If the b,t, and tau Yukawas are equal at the GUT scale then |\Vcb| is predicted and the top quark mass is constrained to lie in the range m_{t}= 179 ± 4 GeV.

Source Postscript References Related Work

**Authors:** Greg W. Anderson.

*Physics Letters*** B295**: 32-36 (1992),
hep-ph/9209258.

In the standard scenario, the electroweak phase transition is a first order phase transition which completes by the nucleation of critical bubbles. Recently, there has been speculation that the standard picture of the electroweak phase transition is incorrect. Instead, it has been proposed that throughout the phase transition appreciable amounts of both broken and unbroken phases of SU(2) coexist in equilibrium. I argue that this can not be the case. General principles insure that the universe will remain in a homogenous state of unbroken SU(2) until the onset of critical bubble production.

Source Postscript References Related Work

in Proc. of the First Yale-Texas Workshop on Baryon Number
Violation at the Electroweak Scale, New Haven, CT, Mar 19-21, 1992
(World Scientific).

hep-ph/9206245.

In the standard scenario, the electroweak phase transition is a first order phase transition which completes by the nucleation of critical bubbles. Recently, there has been speculation that the standard picture of the electroweak phase transition is incorrect. Instead, it has been proposed that throughout the phase transition appreciable amounts of both broken and unbroken phases of SU(2) coexist in equilibrium. I argue that this can not be the case. General principles insure that the universe will remain in a homogenous state of unbroken SU(2) until the onset of critical bubble production. In addition, an analytic treatment of the one Higgs doublet, electroweak phase transition in the standard model and minimal extensions is reviewed. Results from the thin wall approximation are compared to results obtained using the Lindes' action. Perhaps the most important quantitative result we can get from an analysis of the phase transition is determination of < phi >

_{T}when the phase transition completes. For Higgs boson masses above the current experimental limit, the thin wall approximation determines the value of < phi > at the end of the phase transition to an accuracy of better than three percent.

**Authors:** Greg W. Anderson and L. Hall.

*Physical Review*** D45**: 2685-2698, 1992.

We give an analytic treatment of the one Higgs doublet, electroweak phase transition which demonstrates that the phase transition is first order. The phase transition occurs by the nucleation of thin walled bubbles and completes at a temperature where the order parameter, < phi >

_{T}is significantly smaller than it is when the origin becomes absolutely unstable. The rate of anomalous baryon number violation is an exponentially sensitive function of < phi >_{T}. In very minimal extensions of the standard model it is quite easy to increase < phi >_{T}so that anomalous baryon number violation is suppressed after the completion of the phase transition. Hence, baryogenesis at the electroweak phase transition is tenable in minimal extensions of the standard model with one Higgs doublet.

LBL preprint LBL-31169, University of California, Berkeley Ph.D. Thesis.

An analytic treatment of the one Higgs doublet, electroweak phase transition is given. The phase transition is first order, occurs by the nucleation of thin walled bubbles, and completes at a temperature where the order parameter, < phi >

_{T}, is significantly smaller than it is when the origin becomes absolutely unstable. The rate of anomalous baryon number violation is an exponentially sensitive function of < phi >_{T}. In very minimal extensions of the standard model it is quite easy to increase < phi >_{T}so that anomalous baryon number violation is suppressed after completion of the phase transition. Hence baryogenesis at the electroweak phase transition is tenable in minimal extensions of the standard model. In some cases additional phase transitions are possible. For a light Higgs boson, when the top quark mass is sufficiently large, the state where the Higgs field has a vacuum expectation value < phi > = 246 GeV is not the true minimum of the Higgs potential. When this is the case, and when the top quark mass exceeds some critical value, thermal fluctuations in the early universe would have rendered the state < phi > = 246 GeV unstable. The requirement that the state < phi >_{T}= 246 GeV is sufficiently long lived constrains the masses of the Higgs boson and the top quark. Finally, we consider whether local phase transitions can be induced by heavy particles which act as seeds for deformations in the scalar field. Semi-classical reasoning suggests that, when a particle receives a contribution to its mass from the vacuum expectation value of a scalar, under certain conditions, the ground state of particle number one contains a `dimple' or shallow scalar field condensate around the particle. We argue that this is not the case. A careful analysis, taking into account quantum mechanics, shows that the semi-classical approximation is a poor one. We find that there are no energetically favored one-particle dimple solutions for perturbative couplings.

**Authors:** Greg W. Anderson L. Hall and S. Hsu.

*Physics Letters*** B249**: 505-510 (1990).

Semi-classical reasoning suggests that, when a particle receives a contribution to its mass from the vacuum expectation value of a scalar, under certain conditions the ground state of particle number one is not just a single particle, but rather is a state where a `dimple' or shallow scalar field condensate forms around the particle. We argue that this is not the case. A careful analysis, taking into account quantum mechanics, shows that the semi-classical approximation is a poor one. We find that there are no energetically favored one-particle dimple solutions for perturbative coupling.

**Authors:** Greg W. Anderson.

*Physics Letters*** B243**: 265-270, (1990).

In the standard model, when the top quark mass is sufficiently large, the state where the Higgs field has a vacuum expectation value < phi > = 246 GeV is not the true minimum of the Higgs potential. When this is the case, and when the top quark mass exceeds some critical value, thermal fluctuations in the early universe would have rendered the state < phi >unstable. The requirement that the state < phi > =246 GeV is sufficienly long-lived constrains the masses of the Higgs boson and top quark. We exclude top quark and Higgs boson masses which have not been excluded by previous limits. We note that similiar considerations could constrain the masses of light Higgs bosons with large couplings to fermions in other models.

**Authors:** Greg W. Anderson and I. Hinchliffe.

Presented at Workshop on Experiments, Detectors and Experimental Areas for
the SSC Berkeley, CA.

Published in
*Berkeley SSC Wkshp.
(QCD184:W61:1987) 228* (World Scientific), LBL-24528.

We comment on 4th generation heavy lepton searches at the SSC, and we study signals and backgrounds for the heavy lepton and associated neutrino final state.

**Authors:** S. Spangler, S. Fuselier, A. Fey and G. Anderson

*Journal of Geophysical Research*, Vol 93, No. A2, Feb. 1988

Home | Physics | Northeastern Illinois University |

Last Updated: Jan. 2000 |