Pos(DIS 2010)135

PoS(DIS 2010)135 ) < > ger | 3 3jet y T | M , p ith the a. The ( 8 . ive trijet 0 < http://pos.sissa.it/ | y | ( ce. e found to be in a reasonable ilab Tevatron proton-antiproton ratios of multi-jet cross sections ) jet transverse momenta based on angular distributions in distributions are also studied. T Dmitry Bandurin, Sabine Lammers) and to oximations. φ r, Barcelona, Spain. If you are going to be p gular correlations in minimum bias ∆ t production and the ratio of inclusive that can be used for tuning of multiple in the detector transverse plane between the ction of the invariant three-jet mass ( φ ∆ g and Related Subjects ne and Claus Buszello for their help preparing this talk. Barcelona is not a bad place to be. 96 TeV using a data set corresponding to an integrated . 1 = s ive Commons Attribution-NonCommercial-ShareAlike Licen √ 100 GeV) for events with leading jet transverse momentum lar collisions collected between April 2002 and February 2006 w > , has been measured as a function of the transverse jet moment ¯ p 2 96TeV at the Fermilab Tevatron Collider. The ratio of inclus 3 / . p T 3 1 p R = . The measurement is performed in three rapidity regions 1 s − collisions at √ and in three regions of the third (ordered in ¯ p ) p 70 GeV, 4 . 2 > 3 < †‡ T | ∗ p y | collisions at ¯ p [email protected] p 6 and 5 million minimum bias . 1 40 GeV, than 150 GeV and wellagreement with separated the jets. measured cross NLO sections. Based QCD on calculations the ar same data set,in we present the ﬁrst measurement of Delivered via Skype for BlackBerry from the Hotel Atena De Ma Speaker. My thanks to the DØ QCD physics group conveners (Don Lincoln, events, based on data taken with the DØ experiment at the Ferm luminosity of 0.7 fb We report the measurement of thethree-jet cross-section for to three-je two-jet cross-sections, as well as acollider. study of an The differential inclusive three-jet cross section as a fun and dijet cross sections, DØ detector. We demonstrate that the distributionthe of leading track and all other tracks is a robust observable ≈ color interaction models. Pseudorapidity correlations of is measured in data are compared to QCD model predictionsFinally, we in present different a appr new way to describe minimum bias events ‡ ∗ † Copyright owned by the author(s) under the terms of the Creat c

stranded due to eruptions of the Eyjafjallajökull volcano, Markus Wobisch, Zdenek Hubacek, Camille Belanger-Champag Louisiana Tech University E-mail: Lee Sawyer DØ results on three-jet production, multijet cross-section ratios, and minimum bias angular correlations XVIII International Workshop on Deep-Inelastic Scatterin April 19 -23, 2010 Convitto della Calza, Firenze, Italy PoS(DIS 2010)135 , n T ) 6, . p 1 max 4, for T < . 2 | 40 GeV, y dp | / < > | 3 jet 8, y . requirements T | − 0 p 2 , ≥ min < σ T min | d p y T ( | p / . ) > φ max T x elements for 2-, 3-, and T p , between all pairs of the rected for hadronization and jj elements for 2-, 3-, and 4-jet trijet and dijet cross sections, dp s calculated in NLOJET++[3] R / e jet algorithm [2] with a cone s represent the statistical uncer- QCD, there are many other pro- ata to theory is shown in Fig. 2. 500GeV, for 3jet ). rain the PDFs. sverse momentum ( ≥ ere obtained using default settings edominates. It is also important to ection as a function of the invariant < ngle, σ ed sprays of hadrons, called jets, are erent Monte Carlo event generators. cone ed for non-perturbative processes, in of jet rapidities ( ge from -3% to 6%, obtained from d ion as a function of the invariant three- on and to the partonic structure of the R 150 GeV. The three-jet mass spectra are max · n properties can be used to test the pre- sums of statistical and systematic uncer- T 3) must have 2 , > p ) = ( nties than the individual cross sections, due 2 96 TeV, collected with the DØ detector and > T and azimuthal angle . < is measured as a function of the leading jet .A detailed description of the D0 detector can p jj 1 max y = 1 ) 2 T R n ratios, and minimum bias angular correlations / − n = p 3 ( s 2 R 2 / 7fb √ . 3 R 30GeV + 7 in rapidity . min 0 T p = ( 2 ) φ ∆ -jet event sample (for 100 GeV) with leading jet + ( n 2 ) > y 3 ∆ T ( p , in the interval p max = T v1.1.3 predictions [7], which include the tree-level matri p jets is larger than twice the cone radius( of the three-jet system, and study the ratio of the inclusive cone R T p 3jet 4 for all three jets) and in three regions of the third jet tran 70 GeV and . collisions at a center-of-mass energy of M 2 SHERPA The results are displayed in Fig. 3, where the inner error bar We measure the differential inclusive three-jet cross sect The ratio of inclusive jet cross sections, While jet production is amenable to tests using pertubative In the jet analyzes presented, we measure the trijet cross-s The data are compared to the perturbative QCD NLO prediction In hadron-hadron collisions, production rates of collimat Jets in the inclusive ¯ p > < p 3 | T y p | 4-jet production, are shown asand solid MSTW2008LO PDFs lines and in by Figs. matchingproduction 3. with the a leading These parton order shower. w matrix which the separation in the plane of rapidity and azimuthal a jet mass for three hard, well separated jets in three regions of 50, 70, and 90 GeV. tainties while the total errortainties. bars represent The the data quadratic areThe compared to the predictions from diff be found in Ref. [1]. Jets are deﬁned by the Run II midpoint con to cancelations of correlated uncertainties. Here in an event, in radius of leading program with MSTW2008NLO[4] PDFs. Theunderlying NLO event prediction is effects, cor withPYTHIA[5] simulations correction using varied tune QW[6]. in The comparison the of ran d is less sensitive to experimental and theoretical uncertai dictions of quantum chromodynamics (QCD) as well as to const shown in Fig. 1. 2. Multijet Measurements sensitive to both the dynamicsinitial-state of hadrons. the fundamental Thus measurements interacti of jet productio cesses at a hadron colliderdevelop in tests which of non-perturbative the QCD heuristicorder pr models to that compare them have in been detail develop to experimental results. mass corresponding to an integrated luminosity of 0 1. Introduction DØ results on three-jetLee production, multijet Sawyer cross-sectio PoS(DIS 2010)135 3jet ) (TeV) (TeV) M T3 3jet3jet MM (TeV) (TeV) + p . T2 1 3jet3jet >40 GeV (x2) >70 GeV >100 GeV − MM T3 T3 T3 + p p p p T1 >150 GeV, |y|<2.4 ) T1 p T3 + p = 1/3 (p 4 region is scaled by F T2 . µ 2 = + p R < T1 µ |y|<2.4 | =0.7 ird jet transverse momenta. y -ordered parton shower [9, | cone T p = 1/3(p matic uncertainty in all three-jet , R µ -1 hose for 2-jet production. All nts are found in the highest THIA event generator (version s from the “Perugia” series of Dé Preliminary . The corrections, Systematic uncertainty NLO pQCD+non-perturbative ree regions of jet rapidities.The total 0.40.4 0.6 0.6 0.8 0.8 1.0 1.0 1.2 1.2 1.4 1.4 of these tunes give very different e use the CTEQ5L PDFs [8]. = 1.96 TeV s L=0.7 fb than what is seen in the data, even for (TeV) (TeV) ere are two different implementations, integrated luminosity of 0.7 fb e NLO calculations with NLOJET++ and 2 3jet3jet 44 33 22 11 0.40.4 0.6 0.6 0.8 0.8 1.0 1.0 1.2 1.2 1.4 1.4 -1-1 / -2-2

ertaintycomes from the 20 MSTW2008NLO

3 1010

3jet

1010 1010 3jet 1010

1010 (pb/TeV) /dM /dM d d (pb/TeV) 1010 σ σ R wn by shaded band. Full lines correspond to ng the scale up and down by a factor of 2. n ratios, and minimum bias angular correlations 3 -ordered one. Both are highly tunable and more than |y|<1.6 ) T (TeV) (TeV) Scale dependence MSTW2008 uncertainty Syst. uncertainty T3 p 3jet3jet >40 GeV MM + p T3 T2 + p |y|<0.8 |y|<1.6 |y|<2.4 (x4) 0.40.4 0.6 0.6 0.8 0.8 1.0 1.0 1.2 1.2 1.4 1.4 T1 (TeV) (TeV) 3jet3jet >150 GeV, p MM T1 = 1/3 (p -1 F p µ = R µ >40 GeV =0.7 T3 cone , R but all predict signiﬁcantly higher ratios -1 2 8 region. b) Three-jet mass cross section in regions of the th |y|<0.8 Systematic uncertainty NLO pQCD+non-perturbative corrections, / . 3 0 a) Three-jet mass cross section in regions of jet rapidities Dé Preliminary >150 GeV, p = 1.96 TeV R 40 GeV region is scaled by a factor of 2 for readability. Syste Data to theory ratio of the three-jet mass cross section in th s T1 < L=0.7 fb p Dé Preliminary, L = 0.7 fb > | y 3 22 55 44 33 11 0.40.4 0.6 0.6 0.8 0.8 1.0 1.0 1.2 1.2 1.4 1.4 -1-1 | -4-4 -2-2 -3-3

1010

3jet

3jet 0.40.4 0.5 0.5 0.6 0.6 0.7 0.7 0.8 0.8 0.9 0.9 1.0 1.0 1.1 1.1 1010 1010 1010 1010

In addition, the data are compared to predictions from the PY In Fig. 3 the data are compared to PYTHIA tunes which use the 1010

(pb/TeV) /dM /dM d d (pb/TeV) 1010 1010 1010 p

σ 1.81.8 1.61.6 1.41.4 1.21.2 1.01.0 0.80.8 0.60.6 0.40.4 0.20.2 Data/Theory Data/Theory 10]. These aretunes tune [12], “Professor the pT0” tunes [11]results “Perugia and for hard” two and extreme “Perugia tune soft”. All a factor of 4 for readability. Systematicbin uncertainty in is sho The mass bins is shown byMSTW2008 PDFs. shaded In band. both ﬁgures, Full the lines dataset correspond corresponds to to an th the NLO calculations with NLOJET++ and MSTW2008 PDFs. No eve eigenvectors. The scale uncertainty is determined by varyi Figure 2: systematic uncertaintyis shownby a shadedband. The PDF unc the softest tune from the Perugia series. 50 tunes are provided in PYTHIA v6.422. All tunes studies her Figure 1: 6.422). The matrix elementsadditional jet implemented emissions in are produced PYTHIA by a area parton virtuality-ordered only shower. parton Th t shower and a DØ results on three-jetLee production, multijet Sawyer cross-sectio PoS(DIS 2010)135 T T p p 5 GeV . 0 > 50, for two nd to satisfy / T p π ent the statistical the leading jet = 90 GeV and all other tracks in e require that the event Tmin p lead T ect with exactly two muons p SHERPA tune Pro-pT0 tune Perugia hard tune Perugia soft PYTHIA: me tunes and models imple- n the track with the largest 100 200 300 500 lision and possibly initial state ra- evelopment of showers in jets, the -ordered parton shower) are compared are required to have bative QCD convoluted with PDFs, d the angular separation in the de- least ﬁve tracks associated to each variable is then compared to several ertex is computed. The background- 1, historically the region for which T p ft QCD processes”) are not amenable s require comparison to experimental ed from the primary vertex by at 5 cm, < | important for comparison to models. The ibution) is then normalized to the number η | = 70 GeV ratic sums of statistical and systematic uncertainties. n ratios, and minimum bias angular correlations Tmin 4 p ranges: (GeV) | η Tmax | p distribution is shown in Fig. 4, in bins of 100 200 300 500 φ Dé preliminary (for three tunes using the ∆ . η PYTHIA -1 , between the leading track in the events ( = 50 GeV requirements for the other jets. The inner error bars repres φ of trijet and dijet cross sections, measured as a function of and 0. Approximately 4.3 million minimum bias vertices were fou ∆ . 2 Tmin / 2 min p 3 = 0.7 fb T R int p < L | SHERPA η | 100 200 300 500 The ratio 2 GeV, both associated with the primary vertex of the event. W > 0 T ) for different 0.2 0.1

0.15 0.05

In order to create a sample of minimum bias events, we ﬁrst sel For each minimum bias vertex, the angular separation betwee We have compared the distribution obtained from data with so While jet production is described reasonably well by pertur

2-jet 3-jet 3/2

/ / =

R max σ σ T p mented in PYTHIA version 6.421 in two to the data. 3. Angular Correlations in Minimum Bias Events a variety of topics (usually groupedto under a the pertubrative heading QCD of “so calculation.underlying events These produced would from include the thediation, remnant d minimum bias partons events, of etc. aresults Models col in of these order processe to tunetector the transverse model plane, parameters. Wethe have event, as studie a way toMonte characterize Carlo minimum tunes bias and events. models. This with these selection requirements. different ranges of leading track The predictions of and every other track associated with the same minimum bias v ( uncertainties while the total error bars represent the quad contains one more additional minimumvertex. These bias minimum vertices, bias with vertices are at and required to to be separat within 20 cmand of to be the within center of the detector. All tracks subtracted distribution (using a polynomial ﬁtof to tracks, the as distr only the shapenormalized, of the background-subtracted resulting distribution is Figure 3: DØ results on three-jetLee production, multijet Sawyer cross-sectio PoS(DIS 2010)135 , 2 / T 3 p R edited . T n II, p une and model , 463 (2006). 565 φ ∆ ction of the leading jet hich is an update of the First | < 2| < 2 ns at a center of mass energy ηη ee-jet mass cross-section, and of the third jet. The ratio new variable for investigating T p s the Generalized Area Law color relation between tracks. This new nd the Generalized Area Law model cts the shape signiﬁcantly and where increasing the tuning power. o models and tunes. While some some f the s, 2000) p. 47, see Section 3.5. 4 (a) and (b), it is clear that the extended ter than other, none described the distri- = 1.96 TeV Data PYTHIA Tune A PYTHIA Tune P0 PYTHIA GAL s DO Preliminary D / ranges are shown in Fig. 4 (a) and (b). Tune A n ratios, and minimum bias angular correlations | η 5 subtracted, normalised | normalised | subtracted, subtracted, φφ ∆∆ -ordered showers. They both use the color-annealing 0 0.5 1 1.5 2 2.5 3 0 T to the leading track in the same minimum bias vertex, for (a)

0.01

min 0.06 0.05 min 0.04 0.03 0.02

/50) ) / ( / ) N − (N )/ N − (N

π 2, the region accessible with the D0 detector. The com- T T T T φ ∆ < | η | φ ∆ | < 1| < 1 requirements on the jets, as a function of the leading jet ηη min Proceedings of the Workshop: QCD and Weak Boson Physics in Ru T p 0. Error bars include systematic uncertainties. (D0 Collaboration), Nucl. Instrum. Methods Phys. Res. A distribution, subtracted and normalized, to three PYTHIA t . , in 2 φ ∆ < | et al. Data PYTHIA Tune A PYTHIA Tune P0 PYTHIA GAL et al. η | = 1.96 TeV s of trijet and dijet cross section in hadron-hadron collisio DO Preliminary D / 2 / 96 TeV. The three-jet mass cross section is presented as a fun The normalized distribution of 3 . R 1 subtracted, normalised | normalised | subtracted, subtracted, -ordered parton showers, while tune P0 is a more recent tune w 0 and (b) φφ . 2 = ∆∆ 1 by U. Baur, R.K. Ellis, and D. Zeppenfeld, (Batavia, Illinoi Q s In addition to our multijet results, we also have presented a In summary, we have presented the ﬁrst measurement of the thr 0 0.5 1 1.5 2 2.5 3 0 <

√

0.01 min 0.08 0.07 min 0.03 0.02 0.06 0.05 0.04

/50) ( / ) N − (N )/ N − (N

π [1] V. M. Abazov [2] G. C. Blazey T T T T η minimum bias and underlying events,observable based allows on discriminative power the between Monte angular Carl cor of the models studied describe thebutions angular well. correlations bet References is presented for various | parison of the data uses Sandhoff-Skands tune (S0) [17] and uses 4. Summary the ratio of for three regions of leading jet rapidity and three regions o tuning data is provided [13], and model for color reconnections. GAL is based on tune S0 but use Figure 4: implementations (Tune A [14], the Perugiaof 0 color tune reconnections (P0) (GAL) [15], [16]) a in those two reconnection model. In comparing the distributions in Fig. the Monte Carlo tunes and models present large differences, DØ results on three-jetLee production, multijet Sawyer cross-sectio reach of the D0 detector allows us to access a region that affe PoS(DIS 2010)135 , 0902 (CDF et al. , 189 (2009). , 122003 (2002). 63 88 ern, arXiv:0906.0075[hep-ph]. Phys. J. C ann, F. Siegert and J. Winter, JHEP , 375 (2000). .3418). , 1819 (1988). F. Abe, 12 61 n ratios, and minimum bias angular correlations (2005) 129 , 238 (2001). , 129 (2005). 6 39 135 , Snowmass, Colorado, 30 Jun - 21 Jul 2001, pp P501 C 39 Proceedings of APS / DPF / DPB Summer Study on the , 2330 (1990). (1999) 364 D 41 , 094002 (2003); Z. Nagy, Phys. Rev. Lett. B 452 D 68 (TeV4LHC QCD Working Group), arXiv:hep-ph/0610012. , Comput. Phys. Commun. (CTEQ Collaboration), Eur. Phys. J. C , arXiv:hep-ph/0604120. et al. (CDF Collaboration), Phys. Rev. Lett. et al. et al. et al. et al. Future of Particle Physics (Snowmass 2001) 007 (2009). Collaboration), Phys. Rev. [3] Z. Nagy, Phys. Rev. [4] A. D. Martin, W. J. Stirling, R. S. Thorne and G. Watt, Eur. [5] T. Sjöstrand [6] M. G. Albrow [7] T. Gleisberg, S. Hoche, F. Krauss, M. Schonherr, S. Schum [8] H.L. Lai [9] T. Sjostrand and P. Z. Skands, Eur. Phys. J. C DØ results on three-jetLee production, multijet Sawyer cross-sectio [10] C. Buttar [11] A. Buckley, H. Hoeth, H. Lacker, H. Schulz and E. von Segg [12] P. Z. Skands, arXiv:0905.3418[hep-ph]. [13] F. Abe, [14] R. D. Field (CDF Collaboration), in the [15] P. Z. Skands, “The Perugia Tunes,” (arXiv:hep-ph/0905 [16] J. Rathsman, Phys. Lett. [17] T. Sjostrand and P. Z. Skands, Eur. Phys. J.