Inclusive distributions at the LHC as predicted from the DPMJET-III model with chain fusion

Transcription

1 Inclusive distributions at the LHC as predicted from the DPMJET-III model with chain fusion F.Bopp, R.Engel, J.Ranft and S.Roesler () DPMJET III () Chain fusion in DPMJET III (3) dn/dη cm distributions (4) N part dependence (5) Scaling behaviour (6) Transverse momentum distributions in central collisions

2 () DPMJET III Status and problems. h h collisions: PHOJET in DPMJET III R.Engel Z.Phys. C66, 3, (995) R.Engel and J.Ranft Phys. Rev. D54, 444, (996) h A, A A collisions: DPMJET III S.Roesler, R.Engel and J.Ranft Proc. of Monte Carlo (Lisboa), Springer, p.33 () Not implemented in DPMJET III: Jet quenching

3 7 6 5 (b) CDF 8 GeV UA5 546 GeV UA5 GeV UA5 53 GeV PHOJET pppiosnspt π p--p GeV PHOJET π p--p GeV PHENIX dn ch /dη 4 3 Ed 3 σ/d 3 p (mb/gev ).. e pseudorapidity η e p t [GeV/c] (left) Energy-dependence of charged particle pseudorapidity density in p p collisions. PHOJET is compared to data from different colliders (right) Transverse momentum distribution of π mesons as measured in p p collisions at s = GeV by the PHENIX collaboration at RHIC compared to the calculation by PHOJET

4 () Percolation of hadronic strings, DPMJET III Using the original DPMJET III with enhanced baryon stopping and a centrality of to 5 % we compare to some multiplicities measured in Au Au collisions at RHIC. At (s) = 3 GeV DPMJET III gives N ch = 63, BRAHMS finds N ch = 386 ± 3. Again at (s) = 3 GeV DPMJET III gives a plateau dn ch /dη η= = 968, BRAHMS finds dn ch /dη η= = 553 ± 36, PHOBOS finds dn ch /dη η= = 63 ± 4 and PHENIX finds dn ch /dη η= = 6 ± 4.

5 Percolation of hadronic strings in Dpmjet III More details on percolation and chain fusion, see Pajares et al. We consider only the percolation and fusion of soft chains (transverse momenta of both chain ends below a cut off p fusion = GeV/c The condition of percolation is, that the chains overlap in transverse space. We calculate the transverse distance of the chains L and K R L K and allow fusion of the chains for R L K R fusion =.75 fm. The chains in DPMJET are fragmented using the Lund code

6 Only the fragmentation of color triplet antitriplet chains is available in Jetset, however fusing two arbitrary chains could result in chains with other colors. Therefore, we select only chains for fusion, which again result in triplet antitriplet chains. (i)a q q plus a q 3 q 4 chain become a q q 3 q q 4 chain. (ii)a q q q 3 plus a q 4 q chain become a q q 4 q 3 chain. (iii)a q 3 q q plus a q 4 q plus a q 3 q 5 chain become a q 4 q q 5 chain. (iv)a q 4 q plus a q 5 q 3 plus a q 5 q chain become a q 4 q 3 chain.

7 The expected results of these transformations are a decrease of the number of chains. Even when the fused chains have a higher energy than the original chains, the result will be a decrease of the hadron multiplicity N hadrons. In reaction (i) we observe new diquark and anti diquark chain ends. In the fragmentation of these chains we expect baryon antibaryon production anywhere in the rapidity region of the collision. Therefore, (i) helps to shift the antibaryon to baryon ratio of the model into the direction as observed in the RHIC experiments.

8 (3) dn/dη cm distributions auau3etacmphobos3 PHOBOS 3 GeV PHOBOS 3 GeV PHOBOS 3 GeV PHOBOS 3 GeV PHOBOS 3 GeV PHOBOS 3 GeV DPMJET 3 GeV -6 % DPMJET 3 GeV 6-5 % DPMJET 3 GeV 5-5 % DPMJET 3 GeV 5-35 % DPMJET 3 GeV % 6 dn/detacm eta cm Pseudorapidity distributions of charged hadrons in Au Au collisions at (s)= 3 GeV for centralities 5 % up to 4 5 %. The data points are from the PHOBOS Collaboration

9 We apply DPMJET III with chain fusion to central Pb Pb collisions 3 5 etacmauaupbpb PHOBOS GeV PHOBOS 3 GeV PHOBOS 6.4 GeV DPMJET Au-Au GeV -6 % DPMJET Au-Au 3 GeV -6 % DPMJET Au-Au 6.4 GeV -6 % DPMJET Pb-Pb 55 GeV - % DPMJET Pb-Pb GeV - % DPMJET Pb-Pb 7 GeV - % dn ch /dη cm η cm Pseudorapidity distributions of charged hadrons in Au Au collisions at (s)=, 3 and 6.4 GeV for centralities 6 % and for Pb Pb collisions at 55, and 7 GeV for centralities %. The data points are from the PHOBOS Collaboration

10 etacmnpbpb55 4 DPMJET Pb-Pb 55 GeV - % DPMJET Pb-Pb 55 GeV - % DPMJET Pb-Pb 55 GeV -3 % DPMJET Pb-Pb 55 GeV 3-4 % DPMJET Pb-Pb 55 GeV 4-6 % 5 etacmpbpb55 DPMJET Pb-Pb 55 GeV - % DPMJET Pb-Pb 55 GeV - % DPMJET Pb-Pb 55 GeV -3 % DPMJET Pb-Pb 55 GeV 3-4 % DPMJET Pb-Pb 55 GeV 4-6 % dn ch /dη cm 5 [dn ch /dη cm ] / N part / η cm η cm

11 A(N) arbitrary units... pbpbmbmul Pb-Pb 55 GeV % Pb-Pb 55 GeV etacm <.5 % Pb-Pb 55 GeV - % Pb-Pb 55 GeV - % etacm <.5 % Pb-Pb GeV % Pb-Pb GeV etacm <.5 % Pb-Pb 7 GeV % Pb-Pb 7 GeV etacm <.5 % e N Multiplicity distributions in minimum bias and % central collisions in Pb Pb collisions in the full η cm range and for η cm.5 (from DPMJET-III).

12 (4) N part dependence dn AA /dη cm (we consider only the behaviour at η cm = ) shows a simple scaling behaviour in terms of the number of participants N part. In the DPMJET III Monte Carlo we know the number of participants in each collision event. We plot dnaa dη cm / N part as function of N part or as function of E CM.

13 pbpbscaling6 dn AA ch /deta/n part / DPMJET AuAu GeV PHENIX AuAu GeV DPMJET AuAu 3 GeV DPMJET AuAu 6.4 GeV DPMJET AuAu 9.6 GeV DPMJET PbPb 55GeV DPMJET PbPb 7GeV DPMJET PbPb GeV N part dn AA dη cm / N part as function of N part. The DPMJET III calculations are for Au Au at RHIC energies and for Pb Pb at LHC energies.

14 pbpbscaling6 DPMJET centrality -5 DPMJET centrality 5-5 DPMJET centrality 5-5 DPMJET centrality 5-35 DPMJET centrality DPMJET centrality 45-6 dn AA ch /deta/n part / E cm dn AA dη cm / N part as function of E CM. The DPMJET III calculations are for Au Au at RHIC energies and for Pb Pb at LHC energies.

15 Scaling behaviour Limiting fragmentation hypothesis in hadron hadron collisions Beneke, Chou, Yang, Yen, Phys.Rev. 88,59 (969) E d3 σ d 3 p = d3 σ dyd p = G(y, p, s) G(y, p, s) s G(y, p ) for y < L G(p ) for L < y < Y L G(Y y, p ) for Y L < y G(y, p ) universal function in both fragmentation regions Today: G(p ) for L < y < Y L contradicted by rise of rapidity plateau

16 Proton Proton collisions 5 4 (a) p+p 9 GeV 546 GeV GeV 53 GeV 5 4 pp54lim p-p 6.8 GeV p-p GeV p-p 546 GeV p-p 9 GeV dσ/dη/σ inel 3 dn/dη cm 3 Fragmentation η-y beam η cm -y beam (left) data from ISR and SPS show limiting fragmentation (right) DPMJET-III in this energy range has also limiting fragmentation

17 5 pp54diff p-p GeV p-p 4 GeV 5 pp547diff p-p GeV p-p 4 GeV dn/dη cm dn/dy cm η cm -y beam y cm -y beam DPMJET lim. frag. in limited energy range, LHC curves different but notice the differences are outside the fragmentation region (left) Pseudorapidity distribution (right) Rapidity distribution

18 Nucleus Nucleus collisions Number of participants: N part = N A + N B Number of collisions: N coll = N (needed for collision scaling) Limiting fragmentation in nuclear collisions A + A X R(y, p, s) = d 3 N (N part /)dyd p R(y, p, s) s { R(y, p ) for y < L R(Y y, p ) for Y L < y R(y, p ) universal function in both fragmentation regions

19 dn ch /dη/ N part / (d) AuAu CuCu (Prelim.) AuAu 3 CuCu 6.4 (Prelim.) AuAu 6.4 AuAu 9.6 [dn/dη cm ]/(Npart/) auaucuc6p54 Au-Au 9.6 GeV -6 % Au-Au 6.4 GeV -6 % Cu-Cu 6.4 GeV -6 % Au-Au 3 GeV -6 % Au-Au GeV -6 % Cu-Cu GeV -6 % η - y beam η cm -y beam (left) Data for limiting fragmentation in Au Au and Cu Cu collisions of different energies (-6 % central) (right)dpmjet III results for the same collisions

20 / part dn/dη/ N 4 3 GeV 3 GeV 6.4 GeV 9.6 GeV a) Au+Au -6% PHOBOS η b) Au+Au 35-4% Data for limiting fragmentation in Au Au collisions (left) ( 6 %) centrality (right) (35 4 %) centrality η

21 8 auauc6p54 Au-Au 9.6 GeV -6 % Au-Au 6.4 GeV -6 % Au-Au 3 GeV -6 % Au-Au GeV -6 % Au-Au 55 GeV -6 % Au-Au GeV -6 % Au-Au 7 GeV -6 % 8 auauc354p54 Au-Au 9.6 GeV 35-4 % Au-Au 6.4 GeV 35-4 % Au-Au 3 GeV 35-4 % Au-Au GeV 35-4 % Au-Au 55 GeV 35-4 % Au-Au GeV 35-4 % Au-Au 7 GeV 35-4 % [dn/dη cm ] / (N part /) 6 4 [dn/dη cm ] / (N part /) η cm -y beam η cm -y beam DPMJET III results for limiting fragmentation in Au Au collisions at two different centralities (left) ( 6 %) centrality (right) (35 4 %) centrality

22 (6) Chain chain interactions in DPMJET III Density of chains in transverse x - y space, one central Au Au event ********************************************* ********************************************* **************6**7**4******************* ***********3**6*5*5*3**************** ***********9*36*75*8*77*4*7**5************ ********3*3*7959*9*5*49**8************ ********4*4*79387*3**4*********** *********6*8*7*86*85*55***7************ ***********9*3*64*5*3*7**6************** ***********4*4*9*5*3**3****************** *****************6************************** ********************************************* ********************************************* The transverse force on chain is proportional to density gradient of chains The chain gets an additional transverse velocity proportionat to this force

23 (6.) Transverse momentum distributions according to DPMJET-III, Protons and π + auauphenixptinvpip55 PHENIX Au-Au GeV pi+ DPMJET Au-Au GeV pi+ PHENIX Au-Au GeV p DPMJET Au-Au GeV p d 3 N/d 3 p GeV pt

24 (6.) Average transverse momenta as function of N part, π + and protons auauphenixptavpip5 auauphenixptavp5. PHENIX Au-Au GeV pi + etacm= BRAHMS Au-Au GeV pi + etacm= BRAHMS Au-Au GeV pi + etacm= DPMJET Au-Au GeV pi + etacm <.5 DPMJET Au-Au GeV pi +.5 < etacm <.5.. PHENIX Au-Au GeV p etacm= BRAHMS Au-Au GeV p etacm= BRAHMS Au-Au GeV p etacm= DPMJET Au-Au GeV p etacm <.5 DPMJET Au-Au GeV p.5 < etacm < <pt> <pt> N part N part

25 (6.3) Proton to pion ratios as function of p auauphenixpdpip5.4 PHENIX GeV p/pip - % DPMJET GeV p/pip -5% etacm <.5 DPMJET GeV p/pip 4-6% etacm <.5 DPMJET GeV p/pip 6-9% etacm <.5. p/pip p t

26 Conclusions DPMJET III works stable and fast for any nuclear collisions Simple N part dependence Excellent limiting fragmentation in fragmentation region Main application of model: h h collisions, h A collisions and nuclear collisions of light nuclei Not implemented: jet quenching No good implementation: Elliptic flow