arXiv subjects

R. Arnowitt

Publications and source records attributed to R. Arnowitt.

At least 37 records · Page 2Linked to original sources

arXiv2002

Cosmology in Horava-Witten M-Theory

The cosmology of the Horava-Witten M-Theory reduced to five dimensions retaining the volume modulus is considered. Brane matter is considered as a perturbation on the vacuum solution, and the question of under what circumstances does the theory give rise to the standard RWF cosmology is examined. It is found that for static solutions, one obtains a consistent solution of the bulk field equations and the brane boundary conditions only for pure radiation on the branes. (A similar result holds if additional 5-branes are added in the bulk.) If one stabilizes the fifth dimension in an ad hoc manner, a similar inconsistency still occurs (at least for a Hubble constant that has no dependence on y, the fifth dimension.) Within this framework, the possibility of recovering the RWF cosmology still remains if the volume modulus and /or the distance between branes becomes time dependent, under which circumstances the Hubble constant must then depend on y (unless the fifth dimension and volume modulus expand at precisely the same rate).

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arXiv2002

Quark, Lepton and Neutrino Masses In Horava-Witten Inspired Models

Horava-Witten M-Theory offers new ways in achieving the quark and lepton mass hierarchies not naturally available in supergravity unified models. In previous work, based on a torus fibered Calabi-Yau manifold with a del Pezzo base dP_7,a three generation SU(5)model with Wilson line breaking to the Standard Model was constructed. It was seen that if the additional 5- branes clustered near the distant orbifold plane, it was possible that such models could generate the observed hierarchies of quark masses without undue fine tuning. We update these results here and extend them to include the charged leptons. A new mechanism for generating small neutrino masses (different from the ususal seesaw mechanism)arises naturally from a possible cubic holomorphic term in the Kahler potential when supersymmetry is broken. We show that the LMA solution to neutrino masses can occur, with a good fit to all neutrino oscillation data. The model implies the existance of the μ-> e γdecay even for universal slepton soft breaking masses, at rates accessible to the next round of experiments.

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arXiv2002

Dark matter and Consequences of SUSY

We examine here the constraints from the amount of relic density of neutralino dark matter and other experiments have on the SUSY parameter space for the mSUGRA model and for models with non-universal soft breaking at the GUT scale. In mSUGRA, the allowed amount of dark matter restricts the SUSY parameter space to a narrow band in m_0 - m_{1/2} (except at very large \tanβ). The Higgs mass and b-> sγconstraints produce a lower bound of m_{1/2}>~{\sim} 300GeV and if the muon magnetic moment anomaly can be interpreted as a 3σdeviation from the Standard Model, one also obtains an upper bound of m_{1/2} <~900 GeV, making the SUSY spectrum well accessible to the LHC. The B_s->μμdecay is seen to be accessible to the Tevatron Run2B with 15 fb^{-1} for \tanβ>~30. However, only parts of the spectrum will be accessible to the NLC if it's energy is below 800GeV. Non-universal soft breaking opens new regions of parameter space. Thus the m_{1/2} lower bound constraint of b->sγand also the Higgs mass can be reduced greatly if the gluino mass is assumed larger at the GUT scale (allowing for a lighter gaugino spectrum), and non-universal Higgs soft breaking masses at the GUT scale can open new allowed regions at relatively low m_{1/2} and high m_0 where dark matter detection cross sections may be increased by a factor of ten or more.

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arXiv2002

SUSY Dark Matter: Closing The Parameter Space

We consider here the constraints in SUGRA models on the SUSY parameter space due to current experimental bounds on the light Higgs mass m_h, the b-> s gamma decay, the amount of neutralino cold dark matter Omega h^2, and the muon magnetic moment. Models with universal soft breaking (mSUGRA) and non-universal gaugino or Higgs masses at M_G are examined. For mSUGRA, the m_h, b->s gamma and Omega h^2 constraints imply a lower bound on the gaugino mass of m_{1/2}>~300GeV implying the gluino and squarks have mass >~700GeV, and the neutralino >~120GeV. The current status of the Brookhaven muon g - 2 experiment is reviewed, and if the Standard Model (SM) contribution evaluated using the e^+ + e^- data is correct, a 2 sigma bound on the deviation of experiment from the SM produces an upper bound on m_{1/2} that eliminates the "focus point" regions of parameter space. Dark matter (DM) detection cross sections range from 5\times10^{-8} pb to 5\times10^{-10} pb which would be accessible to future planned detectors. The SUSY decay B_s->μ^+ +μ^- is seen to be accessible to the Tevatron Run 2B with 15 fb^{-1} luminosity for tanbeta >~30. The most favorable signals of SUSY for linear colliders are stau pair production and neutralino pair production, though it will require an 800GeV machine to cover the full parameter space. Non-universal models can modify some of the above results. Thus a non-universal (heavier) gluino mass at M_G can significantly reduce the lower bound constraints of b\to s gamma and m_h giving rise to a lighter SUSY spectrum. A heavier up Higgs mass can open an additional region with allowed relic density arising from annihilation via the s-channel Z diagram with an O(10) larger DM detector cross section.

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arXiv2002

Detection of B_s->mu mu at the Tevatron Run II and Constraints on the SUSY Parameter Space

A measurement of the branching ratio for the rare decay mode B_s->mu mu at the Tevatron is an opportunity to test various supersymmetric scenarios. We investigate the prospects for studying this mode in Run II and estimate that CDF would be sensitive to this decay for a branching ratio > 1.2 \times 10^{-8} with 15 \invfb (or, if a similar analysis holds for D0, >6.5\times 10^{-9} for the combined data). We calculate the branching ratio in minimal supergravity (mSUGRA) parameter space, and find that tanβ> 30 can be probed. (This mSUGRA parameter space cannot be probed by direct production of SUSY particles at Run II.) Including other experimental constraints on the mSUGRA parameter space, one finds that CDF \bsmumu measurements would be able to cover the full mSUGRA parameter space for tanβ= 50 if the muon g_μ - 2 anomaly exceeds \sim 11 \times 10^{-10}, and about half the allowed parameter space for tanβ= 40. A large branching ratio > 7(14) \times 10^{-8} (feasible with only 2 \invfb) would be sufficient to exclude the mSUGRA model for tanβ\leq 50(55). Dark matter neutralino-proton detection cross sections are examined in the allowed region, and should be large enough to be accessible to future planned experiments. Combined measurements of \bsmumu the Higgs mass m_h and the muon g_μ-2 anomaly would be sufficient to determine the μ>0 mSUGRA parameters (or show the model is inconsistent with the data). We also briefly discuss the \bsmumu decay in R parity violating models. There, for some models, the branching ratio can be large enough to be detected even for small tanβand large \mhalf.

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arXiv2002

Supersymmetry and Dark Matter

We examine supergravity models with grand unification at M_G possessing R parity invariance. Current data has begun to significantly constrain the parameter space. Thus for mSUGRA, accelerator data places a lower bound on m_{1/2} of m_{1/2} >~300 GeV while astronomical data on the amount of relic dark matter narrowly determines m_0 in terms of m_{1/2} (for fixed value of tanbeta and A_0) due to co-annihilation effects. Additional new data could fix the parameters further. Thus the parameter space is sensitive to the muon magnetic moment anomaly, δa_μ, and if δa_μlies 1 σabove its current central value, it would exclude mSUGRA, while if it lies 1σbelow (but is still positive) it pushes the SUSY spectrum into the TeV domain. The B_s ->μ^+ μ^- decay is seen to be accessible to the Tevatron RunII with branching ratio sensitivity of Br[B_s ->μ^+ μ^-] > 6.5\times10^{-9} with 15 fb^{-1}/detector, and a value of 7(14)\times10^{-8} obtainable with 2 fb^{-1} would be sufficient to exclude mSUGRA for tan beta < 50(55). Measurements of B_s ->μ^+ μ^- can cover the full mSUGRA parameter space for tanbeta > 40 if δa_μ> 11\times10^{-10}, and combined measurements of B_s -> μ^+ μ^-, a_μand m_h (or alternately the gluino mass) would effectively determine the mSUGRA parameters for μ> 0. Detector cross sections are then within the range of planned future dark matter experiments. Non-universal models are also discussed, and it is seen that detector cross sections there can be much larger, and can be in the DAMA data region.

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arXiv2002

Dark Matter in SUSY Models

Direct detection experiments for neutralino dark matter in the Milky Way are examined within the framework of SUGRA models with R-parity invariance and grand unification at the GUT scale, M_G. Models of this type apply to a large number of phenomena, and all existing bounds on the SUSY parameter space due to current experimental constraints are included. For models with universal soft breaking at M_G (mSUGRA), the Higgs mass and b\to sγconstraints imply that the gaugino mass, m_{1/2}, obeys m_{1/2} >(300-400)GeV putting most of the parameter space in the co-annihilation domain where there is a relatively narrow band in the m_0 - m_{1/2} plane. For $μ> 0$ we find that the neutralino -proton cross section >~ 10^{-10} pb for m_{1/2} < 1 TeV, making almost all of this parameter space accessible to future planned detectors. For μ< 0, however, there will be large regions of parameter space with cross sections < 10^{-12} pb, and hence unaccessible experimentally. If, however, the muon magnetic moment anomaly is confirmed, then μ>0 and m_{1/2}<~ 800 GeV. Models with non-universal soft breaking in the third generation and Higgs sector can allow for new effects arising from additional early universe annihilation through the Z-channel pole. Here cross sections that will be accessible in the near future to the next generation of detectors can arise, and can even rise to the large values implied by the DAMA data. Thus dark matter detectors have the possibility of studying the the post-GUT physics that control the patterns of soft breaking.

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arXiv2001

Dark Matter Detection Rates In SUGRA Models

Direct detection of Milky Way wimps are discussed within the framework of R-parity conserving SUGRA models with grand unification at M_G. Two questions are discussed: what SUGRA models can account for the DAMA data if this data is confirmed, and is the full SUGRA parameter space accessible to future planned detectors. Experimental constraints of the Higgs mass bound, the b-> sγbound, relic density constraints (including all co-annihilation channels), etc. are imposed. In addition, the effect of the possible muon g - 2 anomaly are examined. For mSUGRA, we find that the Higgs mass and b\to sγconstraint puts a lower bound m_{1/2} > (300 - 400) GeV (i.e. m_{\tildeχ^0_1} > (120 - 160) GeV) for \tanβ< 50, and thus the largest theoretical neutralino-proton cross sections still lie significantly below the DAMA 3σlower bound. (Predictions for \tanβ> 50 become sensitive to the precise value of m_t and m_b.) If in addition one imposes the muon anomaly constraint, μmust be positive and an upper bound of m_{1/2}< 850 GeV for \tanβ< 50 is obtained. More generally, if μ>0 and m_{1/2} < 1 TeV, the cross sections are >~ 10^{-10} pb, and hence this parameter space would be mostly accessible to planned high sensitivity detectors. For non-minimal SUGRA models, the cross sections can be considerably larger, and a simple SU(5) model with non-universal soft breaking in the Higgs and third generation is seen to give cross sections in the DAMA range for \tanβ>~ 15 with m_{\tildeχ^0_1} > 80 GeV, and minimum cross sections >~10^{-10} pb for μ> 0.

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arXiv2001

Effects of the Muon g-2 Anomaly on Dark Matter and Accelerator Physics

The effect of the recently observed 2.6 sigma deviation of the muon anomalous magnetic moment (a_mu = (g_mu -2)/2) from its Standard Model prediction is examined within the framework of supergravity models with grand unification and R parity invariance. The constraints of the Higgs mass bounds, the b -> s gamma bounds (including the large tan beta NLO corrections) and the cosmological relic density of light neutralinos (including all slepton neutralino coannihilation effects) are included in the analysis. For universal soft breaking, the Higgs and b -> s gamma bounds puts a lower bound m_1/2 >~ 300 GeV, most of the parameter space now falling in the co-annihilation region. The 2 sigma lower bound on the magnetic moment anomaly places an upper bound of m_1/2 ~< 800 GeV. It is seen that mSUGRA requires that a_mu ~< 50 \times 10^{-10}. One finds for m_h > 114 GeV, that tan beta > 5(7) for A_0 = 0(-4 m_1/2) and for m_h > 120 GeV, one has tan beta > 15 (10) for A_0 = 0(-4m_1/2). The sparticle spectrum is now much constrained, and the reaches of the Tevatron RUN II, NLC, and LHC for new physics discovery are discussed. Dark matter detection rates are examined, and it is seen that future detectors now would be able to scan most of the parameter space. Models with non-universal soft breaking in the Higgs and third generation of squarks and sleptons are exmained, and it is seen that a new Z s-channel annihilation of neutralinos in the early universe is possible with dark matter detection rates accessible to the next round of detectors.

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arXiv2001

Muon g-2 and Electric Dipole Moments in SUGRA Models

The SUSY contribution to the muon magnetic moment anomaly, a_mu^SUGRA, and the electron electric dipole moment, d_e, is discussed within the framework of a modified mSUGRA model where the magnitudes of the soft breaking masses are universal, but arbitrary phases are allowed. It is shown analytically how the cancellation mechanism can allow for large phases (i.e. theta_B <~ 0.4) and still suppress the value of d_e below its current experimental bound. The dependence of a_mu^SUGRA on the CP violating phases are analytically examined, and seen to decrease it but by at most a factor of about two. This reduction would then decrease the upper bound on m_1/2 due to the lower bound of Brookhaven data, and hence lower the SUSY mass spectrum, making it more accessible to accelerators. At the electroweak scale, the phases have to be specified to within a few percent to satisfy the experimental bound on d_e, but at the GUT scale, fine tuning below 1% is required for lower values of m_1/2. This fine tuning problem will become more serious if the bound on d_e is decreased.

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arXiv2001

SUSY Phases, the Electron Electric Dipole Moment and the Muon Magnetic Moment

The electron electric dipole moment (d_e) and the muon magnetic moment anomaly (a_μ) recently observed at BNL are analyzed within the framework of SUGRA models with CP violating phases at the GUT scale. It is seen analytically that even if d_e were zero, there can be a large Bino mass phase (ranging from 0 to 2 π) with a corresponding large B soft breaking mass phase (of size ~< 0.5 with sign fixed by the experimental sign of a_μ). The dependence of the B phase on the other SUSY parameters, gaugino mass m_{1/2}, \tan β, A_0, is examined. The lower bound of a_μ determines the upper bound of m_{1/2}. It is shown analytically how the existence of a non-zero Bino phase reduces this upper bound (which would correspondingly lower the SUSY mass spectra). The experimental upper bound on d_e determines the range of allowed phases, and the question of whether the current bound on d_e requires any fine tuning is investigated. At the electroweak scale, the phases have to be specified to within a few percent. At the GUT scale, however, the B phase requires fine tuning below the 1% level over parts of the parameter space for low m_{1/2}, and if the current experimental bound on d_e were reduced by only a factor of 3-4, fine tuning below 1% would occur at both the electroweak and GUT scale over large regions of the parameter space. All accelerator constraints (m_h > 114 GeV, b -> s γ, etc.) and relic density constraints with all stau-neutralino co-annihilation processes are included in the analysis.

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arXiv2001

Coannihilation Effects in Supergravity and D-Brane Models

Coannihilation effects in neutralino relic density calculations are examined for a full range of supersymmetry parameters including large \tanβand large A_0 for stau, chargino, stop and sbottom coannihilation with the neutralino. Supergravity models possessing grand unification with universal soft breaking (mSUGRA), models with nonuniversal soft breaking in the Higgs and third generation sparticles, and D-brane models with nonuniversal gaugino masses were analysed. Unlike low \tanβwhere m_0 is generally small, stau coannihilation corridors with high \tanβare highly sensitive to A_0, and large A_0 allows m_0 to become as large as 1TeV. Nonuniversal soft breaking models at high \tanβalso allow the opening of a new annihilation channel through the s-channel Z pole with acceptable relic density, allowing a new wide band in the m_0-m_{1/2} plane with m_{1/2} >~ 400 GeV and $m_0$ rising to 1 TeV. The D-brane models considered possess stau coannihilations regions similar to mSUGRA, as well as small regions of chargino coannihilation. Neutralino-proton cross sections are analysed for all models and it is found that future detectors for halo wimps will be able to scan essentially the full parameter space with m_{1/2} < 1 TeV except for a region with μ< 0 where accidental cancellations occur when 5 ~<\tanβ~< 30. Analytic explanations of much of the above phenomena are given. The above analyses include current LEP bounds on the Higgs mass, large \tanβNLO correction to the b \to s γdecay, and large \tanβSUSY corrections to the b and τmasses.

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arXiv2001

Muon g-2, Dark Matter Detection and Accelerator Physics

We examine the recently observed deviation of the muon g - 2 from the Standard Model prediction within the framework of gravity mediated SUGRA models with R parity invariance. Universal soft breaking (mSUGRA) models, and models with non-universal Higgs and third generation squark/slepton masses at M_G are considered. All relic density constraints from stau-neutralino co-annihilation and large \tanβNLO corrections for b \to sγdecay are included, and we consider two possibilities for the light Higgs: m_h > 114 GeV and m_h > 120 GeV. The combined m_h, b \to sγand a_μ bounds give rise to lower bounds on \tanβand m_{1/2}, while the lower bound on a_μ gives rise to an upper bounds on m_{1/2}. These bounds are sensitive to A_0, e.g. for m_h > 114 GeV, the 95% C.L. is \tanβ> 7(5) for A_0 = 0(-4m_{1/2}), and for m_h > 120 GeV, \tanβ> 15(10). The positive sign of the a_μ deviation implies μ> 0, eliminating the extreme cancellations in the dark matter neutralino-proton detection cross section so that almost all the SUSY parameter space should be accessible to future planned detectors. Most of the allowed parts of parameter space occur in the co-annihilation region where m_0 is strongly correlated with m_{1/2}. The lower bound on a_μ then greatly reduces the allowed parameter space. Thus using 90% C. L. bounds on a_μ we find for A_0 = 0 that \tanβ\geq 10 and for \tanβ\leq 40 that m_{1/2} = (290 - 550) GeV and m_0 = (70 - 300) GeV. Then the tri-lepton signal and other SUSY signals would be beyond the Tevatron Run II (except for the light Higgs), only the \tildeτ_1 and h and (and for part of the parameter space) the \tilde{e}_1 will be accessible to a 500 GeV NLC, while the LHC would be able to see the full SUSY mass spectrum.

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arXiv2001

Supergravity Unification

A review is given of the historical developments of 1982 that lead to the supergravity unified model (SUGRA)with gravity mediated breaking of supersymmetry. Further developments and applications of the model in the period 1982-85 are also discussed. The supergravity unified model and its minimal version (mSUGRA) are currently among the leading candidates for physics beyond the Standard Model. A brief note on the developments from the present vantage point is included.

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arXiv2001

Neutralino Proton Cross Section and Dark Matter Detection

We consider the neutralino proton cross section for detection of Milky Way dark matter for a number of supergravity models with gauge unification at the GUT scale: models with universal soft breaking (mSUGRA), models with nonuniversal soft breaking, and string inspired D-brane models. The parameter space examined includes m_{1/2}<1 TeV and tan β< 50, and the recent Higgs bound of m_h >114 GeV is imposed. (For grand unified models, this bound is to be imposed for all tan β.) All coannihilation effects are included as well as the recent NLO corrections to b\to sγfor large tan β, and coannihilation effects are shown to be sensitive to A_0 for large tan β. In all models, current detectors are sampling parts of the paramater space i. e. tan β>~ 25 for mSUGRA, tan β>~ 7 for nonuniversal models, and tan β>~ 20 for D-brane models. Future detectors should be able to cover almost the full parameter space for μ> 0. For μ< 0, cancellations can occur for m_{1/2} >~ 450 GeV, allowing the cross sections to become ~< 10^{-10} pb for limited ranges of tanβ. (The positions of these cancellations are seen to be sensitive to the value of σ_{πN}.) In this case, the gluino and squarks lie above 1 TeV, but still should be accessible to the LHC if m_{1/2} <1 TeV.

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arXiv2000

Yukawa Textures in Heterotic M-Theory

We examine the structure of the Yukawa couplings in the 11 dimensional Horava-Witten M-theory based on non-standard embeddings. We find that the CKM and quark mass hierarchies can be explained in M Theory without introducing undue fine tuning. A phenomenological example is presented satisfying all CKM and quark mass data requiring the 5-branes cluster near the second orbifold plane, and that the instanton charges of the physical orbifold plane vanish. The latter condition is explicitly realized on a Calabi-Yau manifold with del Pezzo base dP_7.

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arXiv2000

Prospect for Searches for Gluinos and Squarks at a Tevatron Tripler

We examine the discovery potential for SUSY new physics at a p{\bar p} collider upgrade of Tevatron with \sqrt s = 5.4 TeV and luminosity L ~= 4\times 10^{32} cm^{-2}s^{-1} (the Tripler). We consider the reach for gluinos and squarks using the experimental signatures with large missing transverse energy (\met) of jets + \met and 1l + jets + \met (where l=electron or muon) within the framework of minimal supergravity. The Tripler's strongest reach for the gluino is 1060 GeV for the jets + \met channel and 1140 GeV for the 1l + jets + \met channel for 30 fb^{-1} of integrated luminosity (approximately two years running time). This is to be compared with the Tevatron where the reach is 440(460) GeV in the jets + \met channel for 15(30) fb^{-1} of integrated luminosity.

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arXiv2000

Neutralino Proton Cross Sections in SUGRA and D-BRANE Models

We calculate the spin independent neutralino-proton cross section for universal SUGRA, non universal SUGRA and D-brane models with R-parity invariance. The regions of maximum cross section in these models has started to be probed by the current detectors. The minimum cross section generally is >~1\times 10^{-(9-10)}pb and hence will be accessible in the future detectors, barring special regions of parameter space where it can reduce to =~10^{-12}pb. However, the squarks and gluinos will be heavy (>~1 TeV) in the latter case, but still accessible at the LHC.

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