A FORTRAN code for γγ→ZZ in SM and MSSM

Diakonidis, Th.; Gounaris, G. J.; Layssac, J.

doi:10.1140/epjc/s10052-006-0202-6

Cited by 12 publications

(11 citation statements)

References 36 publications

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“…all two-body amplitudes violating the conservation of the total helicity should vanish in MSSM, and tend to constants in SM. A similar behavior has also been observed in the complete 1-loop treatment of γγ → ZZ and γγ → γZ [3,23]. In other words, ratio-of-mass terms, which could be imagined to spoil the exact validity of HC theorem in MSSM, are not generated.…”

Section: Discussionsupporting

confidence: 67%

Remarkable virtual supersymmetric effects inW±production at high energy hadron colliders

2008

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We present a complete 1-loop study of the electroweak corrections to the process ug → dW + in MSSM and SM. The occurrence of a number of remarkable properties in the behavior of the helicity amplitudes at high energies is stressed, and the crucial role of the virtual SUSY contributions in establishing them, is emphasized. The approach to asymptopia of these amplitudes is discussed, comparing the effects of the logarithmic and constant contributions to the mass suppressed ones, which are relevant at lower energies. Applying crossing to ug → dW + , we obtain all subprocesses needed for the 1-loop electroweak corrections to W ± -production at LHC. The SUSY model dependence of such a production is then studied, and illustrations are given for the transverse W ± momentum distribution, as well as the angular distribution in the subprocess center of mass.

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Section: Discussionsupporting

confidence: 67%

Remarkable virtual supersymmetric effects inW±production at high energy hadron colliders

2008

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“…Its realization comes about after the appearance of huge cancellations among the various diagrams. Both, here and in previous work [1,20], we were fascinated to see this happening in detail, so that no terms involving ratios of masses destroy it. This is most tricky, when longitudinal gauge bosons and Yukawa couplings are involved; we intend to examine such cases in the future.…”

Section: Discussionmentioning

confidence: 57%

“…Using (14)(15)(16)(17)(18)(19)(20)(21)(22) and the substitutions (12,13) in (8), we obtain the full contribution arising from the Born terms in Fig.1a, to which the counter terms and self energy contributions have been inserted. All these contributions have the form of 1loop bubbles with two external legs.…”

Section: Introductionmentioning

confidence: 99%

Genuine SUSY signatures fromug→d˜χ˜i+andug→
Gounaris
¹
,
Layssac
²
,
Renard
³

2008
Phys. Rev. D
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11
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8
0
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March 2008 (corrected version)PTA/08-009 arXiv:0803.0813 [hep-ph] Genuine SUSY signatures from ug →dχ AbstractWe analyze the quark-gluon induced process ug →dχ + i , including the one loop electroweak (EW) effects in the minimal supersymmetric model (MSSM). This process is dominated byd L -production and is determined by four helicity amplitudes, three of which are violating helicity conservation, and another one which respects it and is logarithmically enhanced at high energy. Combining this ug →d Lχ + i analysis with a corresponding one for ug → dW + , we obtain simple approximate relations between the two processes, testing the MSSM structure at the amplitude and the cross section levels. These relations become exact at asymptotic energies and, provided the SUSY scale is not too heavy, they may be approximately correct at LHC energies also. In addition to these, we study the 1loop EW corrections to the inclusivedχ + i production at LHC, presenting as examples, the p T and angular distributions. Comparing these to the corresponding predictions for W +jet production derived earlier, provides an accurate test of the supersymmetric assignments. IntroductionIn a previous paper we have shown that the 1loop virtual SUSY EW effects in the process ug → dW + , present a number of remarkable properties [1]. Among them, is the role of SUSY in ensuring the validity of Helicity Conservation (HC) for any two-body process at high energy, to all orders in perturbation theory [2]. By this we mean the fact that at very high energies and fixed angles, the only surviving two-body amplitudes are those where the sum of the initial particle helicities equal to the sum of the final particle helicities [2]. According to HC, these are the only amplitudes that could possibly contribute at asymptotic energies, and in fact receive the logarithmic enhancements extensively studied in [3] and [4]. All the rest must vanish in this limit.These results raised several questions concerning the deeper reasons for the validity of HC, and whether terms involving ratios of masses could possibly violate it 1 . Such questions called for further studies of various explicit processes [1]. Particular among them, are processes involving heavy SUSY-particles in the final state, where establishing of HC is expected to be delayed.Along these lines of thought, we present here an analysis of the process ug →d Lχ + i , which starts from the same initial state as ug → dW + , but its final state involves SUSY partners of dW + . Such a study could provide insights into the SUSY implications, which of course become clearest at the highest energy.Denoting the helicities and momenta of the incoming and outgoing particles in the above process aswe write the corresponding helicity amplitudes as Fχ λuλgλχ . At Born level, these amplitudes are determined by the two diagrams in Fig.1a, characterized by a u-quark exchange in the s-channel, and ad L -squark exchange in the u-channel. Because of the negligible u and d quark masses, the charginos couple only through their...

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“…The reduction of 5-point tensor integrals to 4-point tensor integrals at non-exceptional momenta may be performed by iterative application of (2.5). This was exemplified in [21], and an opensource Fortran code olotic [31] is available. In this sect., we derive a very compact, explicit representation of the tensor coefficients for 5-point functions in a minimal basis, chosen to be free of the metric tensor.…”

Section: An Efficient Reduction Of 5-point Tensor Integralsmentioning

confidence: 99%

Complete algebraic reduction of one-loop tensor Feynman integrals

Fleischer

Riemann

2011

Phys. Rev. D

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We set up a new, flexible approach for the tensor reduction of one-loop Feynman integrals. The 5-point tensor integrals up to rank R ¼ 5 are expressed by 4-point tensor integrals of rank R À 1, such that the appearance of the inverse 5-point Gram determinant is avoided. The 4-point tensor coefficients are represented in terms of 4-point integrals, defined in d dimensions, 4 À 2 d 4 À 2 þ 2ðR À 1Þ, with higher powers of the propagators. They can be further reduced to expressions which stay free of the inverse 4-point Gram determinants but contain higher-dimensional 4-point integrals with only the first power of scalar propagators, plus 3-point tensor coefficients. A direct evaluation of the higherdimensional 4-point functions would avoid the appearance of inverse powers of the Gram determinants completely. The simplest approach, however, is to apply here dimensional recurrence relations in order to reduce them to the familiar 2-to 4-point functions in generic dimension d ¼ 4 À 2", introducing thereby coefficients with inverse 4-point Gram determinants up to power R for tensors of rank R. For small or vanishing Gram determinants-where this reduction is not applicable-we use analytic expansions in positive powers of the Gram determinants. Improving the convergence of the expansions substantially with Padé approximants we close up to the evaluation of the 4-point tensor coefficients for larger Gram determinants. Finally, some relations are discussed which may be useful for analytic simplifications of Feynman diagrams.

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A FORTRAN code for γγ→ZZ in SM and MSSM

Abstract: Through the present paper, the code gamgamZZ is presented, which may be used to calculate all possible observables related to the process γγ → ZZ, in either the Standard Model (SM), or the minimal sypersymmetric standard model (MSSM) with real parameters. †

Cited by 12 publications

References 36 publications

Remarkable virtual supersymmetric effects inW±production at high energy hadron colliders

Remarkable virtual supersymmetric effects inW±production at high energy hadron colliders

Genuine SUSY signatures fromug→d˜χ˜i+andug→
Gounaris
¹
,
Layssac
²
,
Renard
³

2008
Phys. Rev. D
Self Cite
11
0
8
0
View full text Add to dashboard Cite

Complete algebraic reduction of one-loop tensor Feynman integrals

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A FORTRAN code for γγ→ZZ in SM and MSSM

Abstract: Through the present paper, the code gamgamZZ is presented, which may be used to calculate all possible observables related to the process γγ → ZZ, in either the Standard Model (SM), or the minimal sypersymmetric standard model (MSSM) with real parameters. †

Cited by 12 publications

References 36 publications

Remarkable virtual supersymmetric effects inW±production at high energy hadron colliders

Remarkable virtual supersymmetric effects inW±production at high energy hadron colliders

Genuine SUSY signatures fromug→d˜χ˜i+andug→Gounaris1, Layssac2, Renard3 2008Phys. Rev. DSelf Cite11080View full textAdd to dashboardCite

Complete algebraic reduction of one-loop tensor Feynman integrals

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About

Genuine SUSY signatures fromug→d˜χ˜i+andug→
Gounaris
¹
,
Layssac
²
,
Renard
³

2008
Phys. Rev. D
Self Cite
11
0
8
0
View full text Add to dashboard Cite