Sonlu sıcaklık ve yoğunluklarda hadron parametrelerine ortam etkilerinin incelenmesi

TÜBİTAK TBAG Proje114F234Ağır iyon çarpışma deneylerinin analizi, hadron özelliklerinin sonlu sıcaklıklarda ve nükleer madde ortamında incelenmesini gerektirmektedir. Bu özelliklerin incelenebilmesi pertürbatif olmayan yaklaşımlarla mümkündür. Bu yaklaşımlar arasında en başarılı yöntemlerden biri, KRD Toplam Kuralları metodudur. Sonlu sıcaklıkta toplam kuralları bazı yeni özelliklere sahiptir. Bu yeni özelliklerden biri ortamda parçacıkların akımlar ile etkileşmesi olup, hadron spektral fonksiyonunun modifiye edilmesini gerektirir. Diğer yenilik ise sonlu sıcaklıkta maddenin durgun halde olduğu referans sisteminin seçimi sebebiyle, Wilson açılımında Lorentz invaryant olmayan ilave operatörlerin ortaya çıkmasıdır. Bu projenin amacı, sonlu sıcaklık ve yoğunluklarda Termal KRD Toplam Kuralları yöntemini kullanarak, mezon ve baryon parametrelerine ortam etkilerini incelemektir. Pertürbatif katkılar termal kuark propagatörü kullanılarak hesaplanmış, spektral yoğunluğun yok etme ve saçılma kısımları elde edilmiş ve s mertebesinde iki ilmekli katkılar gözönüne alınmıştır. Sonlu sıcaklıklarda 0 durumuna ilaveten ortaya çıkan yeni pertürbatif olmayan katkılar da göz önüne alınarak ağır-hafif skaler, pseudoskaler, ağır-ağır skaler, pseudoskaler, vektör ve aksiyal-vektör mezonların kütle ve leptonik bozunum sabitleri incelenmiştir. Elde edilen ++bu noktadan sonra sıcaklığın artmasıyla, kütle ve bozunma sabitlerinin azalmaya başladığı görülmüştür. Ayrıca T 0 ’ da tensör mezonların kütle ve leptonik bozunum sabitleri, 0 0 * * B BK D DK S S , * * B BK D DK S S ve 1 1 * * B BK D DK S S köşelerinin etkileşim sabitleri, bazı mezonların yapı faktörleri hesaplanmıştır. b , b c( ) ve ' b c( ) ağır baryonlarının yarıleptonik bozunumları ışık konisi KRD toplam kuralları çerçevesinde incelenmiş, ilgili geçişlerin bozunma ve dallanma oranları hesaplanmıştır. Elde edilen sonuçların, yakın gelecekteki LHC deneylerinde test edileceği öngörülmektedir.The analysis of heavy-ion collisions experiments requires investigating hadron properties at finite temperature and nuclear matter medium. To investigate these features non-perturbative approaches are required. Among these approaches, one of the most successful methods is the QCD Sum Rules method. Sum rules method at finite temperature has some new features. One of these new properties is the interaction of the current with the particles in medium requiring the modification of hadron spectral function. The other novelty is the breakdown of Lorentz invariance at finite temperature caused by the choice of the reference frame in which matter is at rest and new operators appear in the Wilson expansion. The aim of this project is to investigate in medium modifications of meson and baryon parameters using Thermal QCD Sum Rules method. Perturbative contributions were calculated using thermal quark propagator, annihilation and scattering parts of spectral density were obtained and the s order of two loops contributions were taken into account. Also, in addition to the 0 case, taking into account the appearing new nonperturbative contributions, heavy-light scalar, pseudoscalar, heavy - heavy scalar, vector and axial-vector mesons masses and leptonic decay constants are studied. According to obtained results, the hadronic parameters remain unchanged up to Τ 100MeV , but after this point, masses and decay constants were started to decrease with increasing temperature. Moreover, at T 0 , tensor mesons masses and leptonic decay constants, 0 0 * * B BK D DK S S , * * B BK D DK S S and 1 1 * * B BK D DK S S coupling constants and some mesons form factors are calculated. Also, heavy b , b c( ) and ' b c( ) baryons semileptonic decays are examined within the framework of light-cone QCD Sum Rules, and decay and branching ratios of related transitions are calculated. The obtained results can be verified in LHC near future experiments

The decay tau ->mu(nu)over-bar(i)nu(i) in the Randall-Sundrum background with localized U(1)(Y) gauge boson

We study the effects of localization of the U(1)(Y) gauge boson around the visible brane and the contributions of the Kaluza-Klein modes of Z bosons on the branching ratio of the lepton flavor violating tau ->mu(nu) over bar (i)nu(i) decay. We observe that the branching ratio is sensitive to the amount of localization of the Z boson in the bulk of the Randall - Sundrum background

Semileptonic B-c to P-wave charmonia transitions within QCD sum rules

The form factors of the semileptonic B-c -> S(AV)l nu (l=tau, mu, e) transitions, where S and AV denote the scalar X-c0 and axial-vector (X-c1,h(c)) mesons, are calculated within the framework of the three-point QCD sum rules. The heavy quark effective theory limit of the form factors is also obtained and compared with the values of the original transition form factors. The results of form factors are used to estimate the total decay widths and branching ratios of these transitions. A comparison of our results on branching ratios with the predictions of other approaches is also presented

Structure of the Xi(b)(6227)(-) resonance

We explore the recently observed Xi(b)(6227)(-) resonance to fix its quantum numbers. To this end, we consider various possible scenarios: It can be considered as either a 1P or 2S excitation of the Xi(b) and Xi'(b)(5935) ground-state baryons with spin-1/2 or the 1P or 2S excitation of the ground-state Xi(b)(5955) with spin-3/2. We calculate the masses of the possible angular-orbital 1P and 2S excited states corresponding to each channel employing the QCD sum rule technique. It is seen that all the obtained masses are in agreement with the experimentally observed value, implying that the mass calculations are not enough to determine the quantum numbers of the state under question. Therefore, we extend the analysis to investigate the possible decays of the excited states into Lambda K-b(0)- and Xi(-)(b) pi. Using the light cone QCD sum rule method, we calculate the corresponding strong coupling constants, which are used to extract the decay widths of the modes under consideration. Our results on decay widths indicate that the Xi(b)(6227)(-) is a 1P angular-orbital excited state of the Xi(b)(5955) baryon with quantum numbers J(P) = 3/2(-)

Semileptonic transition of Sigma(b) to Sigma in light cone QCD sum rules

We use distribution amplitudes of the light Sigma baryon and the most general form of the interpolating current for heavy Sigma(b) baryon to investigate the semileptonic Sigma(b) -> Sigma l(+)l(-) transition in light cone QCD sum rules. We calculate all 12 form factors responsible for this transition and use them to evaluate the branching ratio of the considered channel. The order of branching fraction shows that this channel can be detected at LHC