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Towards a controlled study of the QCD critical point

2008; IOP Publishing; Volume: 35; Issue: 10 Linguagem: Inglês

10.1088/0954-3899/35/10/104098

1361-6471

Ph. de Forcrand,

Particle physics theoretical and experimental studies

A bstract.T he phase di agram ofQ C D ,as a functi on oftem perature T and quark chem i calpotenti al , m ay contai n a cri ti cal poi nt ( E ;T E ) w hose non-perturbati ve nature m akesi ta naturalobjectofl atti ce studi es.H owever,the si gn probl em prevents the appl i cati on ofstandard M onte C arl o techni ques at non-zero baryon densi ty.W e have been pursui ng an approach free ofthe si gn probl em ,w here the chem i calpotenti al i s taken as i m agi nary and the resul ts are Tayl or-expanded i n =T about = 0,then anal yti cal l y conti nued to real .W i thi n thi s approach we have determ i ned the sensi ti vi ty of the cri ti calchem i cal potenti al E to the quark m ass, d( E ) 2 =dm q j E = 0 .O ur study i ndi cates that the cri ti calpoi nt m oves to sm all er chem i calpotenti alas the quark m ass increases.T hi s ndi ng,contrary to com m on w i sdom ,i m pl i esthatthe decon nem entcrossover,w hi ch takes pl ace i n Q C D at = 0 w hen the tem perature i s rai sed,w i l lrem ai n a crossover i n the -regi on w here our Tayl orexpansi on can be trusted.Ifthi s resul t,obtai ned on a coarse l atti ce,i s con rm ed by si m ul ati ons on ner l atti ces now i n progress,then we predi ct that no chiralcri ti calpoi nt w i l lbe found for B .500 M eV ,unl ess the phase di agram contai ns addi ti onaltransi ti ons.