arXiv subjects

Pran Nath

Publications and source records attributed to Pran Nath.

227 records · Page 13Linked to original sources

arXiv1994

Event Rates in Dark Matter Detectors For Neutralinos Including Constraints From The $b\rightarrow sγ$ Decay

Event rates for dark matter detectors in neutralino--nucleus scattering are studied for supergravity unified models, including the constraint arising from the $b\rightarrow sγ$ experiment. The recent experimental measurement of this decay by the CLEO Collaboration leads to strong constraints on the SUSY particle spectrum,and also significantly affects the event rates in dark matter detectors. The analysis given here uses the accurate method for the computation of the relic density and leads to a dip in the event rate when the neutralino mass is $\sim M_Z/2$ due to the $Z$-pole, and similar results hold when the neutralino mass is $\sim m_h/2$ due to the Higgs pole . Implication of these results for dark matter detectors are discussed.

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arXiv1994

Neutralino Event Rates In Dark Matter Detectors

The expected event rates for ${\tilde Z_{1}}$ dark matter for a variety of dark matter detectors are studied over the full parameter space with tan $β\leq$ 20 for supergravity grand unified models. Radiative breaking constraints are implemented and effects of the heavy netural Higgs included as well as loop corrections to the neutral Higgs sector. The parameter space is restricted so that the ${\tilde Z_{1}}$ relic density obeys 0.10 $\leqΩ_{\tilde Z_{1}}h^2\leq 0.35$, consistent with the COBE data and astronomical determinations of the Hubble constant. It is found that the best detectors sensitive to coherrent ${\tilde Z_{1}}$ scattering (e.g. Pb) is about 5-10 more sensitive than those based on incoherrent spin dependent scattering (e.g. CaF). In general, the dark matter detectors are most sensistive to the large tan $β$ and small $m_o$ and $m_{\tilde g}$ sector of the parameter space.

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arXiv1994

Susy Particles

Analysis of the SUSY spectrum in supergravity unified models is given under the naturalness criterion that the universal scalar mass $(m_0)$ and the gluino mass $(m_{\tilde g})$ satisfy the constraint $m_0, m_{\tilde g}$ less than or equal to 1 TeV. The SUSY spectrum is analysed in four different scenarios: (1) minimal supergravity models ignoring proton decay from dimension five operators, (2) imposing proton stability constraint in supergravity models with SU(5) type embedding which allow proton decay via dimension five operators, (3) with inclusion of dark matter constraints in models of type (1), and (4) with inclusion of dark matter constraint in models of type (2). It is found that there is a very strong upper limit on the light chargino mass in models of type (4), i.e., the light chargino mass is less than or equals 120 GeV.

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arXiv1994

$b \rightarrow sγ$ Decay in Supergravity Grand Unification and Dark Matter

An analysis of the $b \rightarrow sγ$ is given in supergravity grand unification using the framework of the radiative breaking of the electro-weak symmetry under three separate sets of constraints:1) neutralino relic density does not overclose the universe,2)p-stability constraint, and 3) the combined constraints of p-stability and COBE data .For case 1 it is found that the CLEO II data on the branching ratio already imposes very strong further constraints on dark matter analyses. For case2 the branching ratio is found to lie in the range (1.5-6.3)x$10^{-4}$ and thus the data does not at present significantly limit the analyses with p-stability constraint. It is shown that improvements by a factor of 3 in the $p \rightarrow\barνK^{+}$ lifetime will reduce SUSY effects to less than O(30$\%$) of the Standard Model value.For case3,the branching ratio lies in the interval (3.1-5.3)x$10^{-4}$, and the SUSY effects lie within (-10$\%$,+50$\%$) of the SM value. Thus as experimental bounds on $B(b \rightarrow sγ)$ improve, one would need in cases 2 and 3 the next-to-leading order QCD corrections to disentangle SUSY effects.

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arXiv1994

Constraints on the minimal supergravity model from the b->s+γdecay

The constraints on the minimal supergravity model from the b->s+γdecay are studied. A large domain in the parameter space for the model satisfies the CLEO bound, BR(b->s+γ)<5.4X10^{-4}. However, the allowed domain is expected to diminish significantly with an improved bound on this decay. The dependence of the b->s+γbranching ratio on various parameters is studied in detail. It is found that, for A_t<0 and the top quark mass within the vicinity of the center of the CDF value, m_t^{pole}=174\pm17 GeV, there exists only a small allowed domain because the light stop is tachyonic for most of the parameter space. A similar phenomenon exists for a lighter top and A_t negative when the GUT coupling constant is slightly reduced. For A_t>0, however, the branching ratio is much less sensitive to small changes in m_t, and α_G.

hep-ph↗

arXiv1994

Unification of Fundamental Interactions in Supersymmetry

A review is given of recent developments on the implications of supergravity grand unification with SU(5)-type proton decay under the condition $M_{H_3} /m_G < 10$ (where $M_{H_3}$ is the Higgs triplet mass) and the naturalness condition that the universal scalar mass $m_0$ and the gluino mass are $<$ 1~TeV. It is shown that the maximum achievable lifetime limits on proton lifetime at Super Kamiokande and ICARUS will exhaust the full parameter space of the model under the constraint $m_{\tilde W_1} >$~100~GeV. Thus the model predicts the observation of either a light chargino with mass $\lappeq$~100~GeV , or the observation of a $\bar νK^+$ mode at Super Kamiokande and ICARUS within the above naturalness constraints.Analysis of the $b \rightarrow sγ$ branching ratio within this model is also discussed. It is shown that there is a significant region of the parameter space where the branching ratio predicted by the model lies within the current experimental bounds. It is pointed out that improved measurements of $B(b\rightarrow sγ)$ will significantly delineate the parameter space of the model and allow for a more stringent determination of their allowed ranges.

hep-ph↗

arXiv1993

Supergravity Models

Theoretical and experimental motivations behind supergravity grand unified models are described. The basic ideas of supergravity, and the origin of the soft breaking terms are reviewed. Effects of GUT thresholds and predictions arising from models possessing proton decay are discussed. Speculations as to which aspects of the Standard Model might be explained by supergravity models and which may require Planck scale physics to understand are mentioned.

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arXiv1993

Supersymmetry and Supergravity: Phenomenology and Grand Unification

A survey is given of supersymmetry and supergravity and their phenomenology. Some of the topics discussed are the basic ideas of global supersymmetry, the minimal supersymmetric Standard Model (MSSM) and its phenomenology, the basic ideas of local supersymmetry (supergravity), grand unification, supersymmetry breaking in supergravity grand unified models, radiative breaking of $SU(2) \times U(1)$, proton decay, cosmological constraints, and predictions of supergravity grand unified models. While the number of detailed derivations are necessarily limited, a sufficient number of results are given so that a reader can get a working knowledge of this field.

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arXiv1993

Testing Supergravity Grand Unification at Future Accelerator and Underground Experiments

The full parameter space of supergravity grand unified theory with $SU(5)$ type $p \rightarrow \barν K$ proton decay is analysed using renormalization group induced electroweak symmetry breaking under the restrictions that the universal scalar mass $m_o$ and gluino mass are $\leq 1$ TeV (no extreme fine tuning) and the Higgs triplet mass obeys $M_{H_3}/M_G < 10$. Future proton decay experiments at SuperKamiokande or ICARUS can reach a sensitivity for the $\barν K$ mode of $(2-5) \times 10^{33}$ yr allowing a number of predictions concerning the SUSY mass spectrum. Thus either the $p \rightarrow\barν K$ decay mode will be seen at these experiments or a chargino of mass $m_{\tilde{W}} < 100$ GeV will exist and hence be observable at LEP2. Further, if $(p \rightarrow \barν K) > 1.5 \times 10^{33}$ yr, then either the light Higgs has mass $m_h \leq 95$ GeV or $m_{\tilde{W}} \leq 100$ GeV i.e. either the light Higgs or the light chargino (or both) would be observable at LEP2. Thus, the combination of future accelerator and future underground experiments allow for strong experimental tests of this theory.

hep-ph↗

arXiv1993

Supergravity Grand Unification, Proton Decay and Cosmological Constraints

Properties and experimental predictions of a broad class of supergravity grand unified models possessing an $SU(5)$-type proton decay and $R$ parity are described. Models of this type can be described in terms of four parameters at the Gut scale in addition to those of the Standard Model i.e. $m_o$ (universal scalar mass), $m_{1/2}$ (universal gaugino mass), $A_o$ (cubic soft breaking parameter) and $\tanβ= / $. Thus the 32 SUSY masses can be expressed in terms of $m_o, m_{1/2}, A_o \tanβ$ and the as yet unknown t-quark mass $m_t$. Gut thresholds are examined and a simple model leads to grand unification consistent with $p$-decay data when $0.114<α_3 (M_z)<0.135$, in agreement with current values of $α_3 (M_Z)$.Proton decay is examined for the superheavy Higgs triplet mass $M_{H_3}<10M_G(M_G\simeq 1.5 \times10^{16}$~GeV) and squarks and gluinos lighter than 1 TeV. Throughout most of the parameter space chargino-neutralino scaling relations are predicted to hold: $2m_{\tilde{Z}_1}\cong m_{\tilde{W}_1}\cong m_{\tilde{Z}_2}, m_{\tilde{W}_1}\simeq(1/4)m_{\tilde{g}}$ (for $μ>0$) or $m_{\tilde{W}_1} \simeq(1/3)m_{\tilde{g}}$ (for $μ<0$), while $m_{\tilde{W}_2}\cong m_{\tilde{Z}_3}\cong m_{\tilde{Z}_4}>>m_{\tilde{Z}_1}$. Future proton decay experiments combined with LEP2 lead to further predictions, e.g. for the entire parameter space either proton decay should be seen at these or the$\tilde{W}_1$ seen at LEP2. Relic density constraints on the $\tilde{Z}_1$ further constrain the parameter space e.g. so that $m_t<165$~GeV, $m_h<105$~GeV, $m_{\tilde{W}_1} <100$~GeV and $m_{\tilde{Z}_1}<50$~GeV when $M_{H_3}/M_G < 6$. (Invited talk at Les Rencontres de Physique de la Vallee D'Aoste}

hep-ph↗

arXiv1993

Cosmological Constraints and SU(5) Supergravity Grand Unification

The predictions of SU(5) supergravity models with radiative breaking constrained by experimental proton decay bounds are discussed. It is shown that cosmological constraints further restrict the parameter space but can be satisfied for a wide range of parameters. It is also shown that no serious fine tuning problems (either at $M_{SUSY}$ or $M_{GUT}$) exist.

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